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 $62.62   5.240%   $65.9013   $65.90   $65.90   $65.90  
  Purchase #2 $132.64   11.769%   $148.2504   $148.25   $148.25   $148.30  
  Purchase #3 $202.84   3.642%   $210.2274   $210.23   $210.25   $210.20  
  Purchase #4 $173.72   13.705%   $197.5283   $197.53   $197.55   $197.50  
  Purchase #5 $124.29   11.393%   $138.4504   $138.45   $138.45   $138.50  
  Purchase #6 $211.53   6.770%   $225.8506   $225.85   $225.85   $225.90  
  Purchase #7 $105.72   3.872%   $109.8135   $109.81   $109.80   $109.80  
  7 purchase totals = $1,013.36       $1,096.0219   $1,096.02   $1,096.05   $1,096.10