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 $202.73   8.352%   $219.662   $219.66   $219.65   $219.70  
  Purchase #2 $57.47   13.228%   $65.0721   $65.07   $65.05   $65.10  
  Purchase #3 $92.84   3.240%   $95.848   $95.85   $95.85   $95.80  
  Purchase #4 $183.61   7.301%   $197.0154   $197.02   $197.00   $197.00  
  Purchase #5 $141.80   9.165%   $154.796   $154.80   $154.80   $154.80  
  Purchase #6 $178.45   5.698%   $188.6181   $188.62   $188.60   $188.60  
  Purchase #7 $184.77   9.855%   $202.9791   $202.98   $203.00   $203.00  
  7 purchase totals = $1,041.67       $1,123.9907   $1,124.00   $1,123.95   $1,124.00