Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $132.66   9.761%   $145.6089   $145.61   $145.60   $145.60  
  Purchase #2 $188.72   13.841%   $214.8407   $214.84   $214.85   $214.80  
  Purchase #3 $238.53   12.666%   $268.7422   $268.74   $268.75   $268.70  
  Purchase #4 $234.29   10.628%   $259.1903   $259.19   $259.20   $259.20  
  Purchase #5 $173.97   5.465%   $183.4775   $183.48   $183.50   $183.50  
  Purchase #6 $207.27   13.679%   $235.6225   $235.62   $235.60   $235.60  
  Purchase #7 $143.93   7.310%   $154.4513   $154.45   $154.45   $154.50  
  7 purchase totals = $1,319.37       $1,461.9334   $1,461.93   $1,461.95   $1,461.90