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 $43.26   7.585%   $46.5413   $46.54   $46.55   $46.50  
  Purchase #2 $153.71   10.588%   $169.9848   $169.98   $170.00   $170.00  
  Purchase #3 $229.96   8.672%   $249.9021   $249.90   $249.90   $249.90  
  Purchase #4 $213.51   3.352%   $220.6669   $220.67   $220.65   $220.70  
  Purchase #5 $231.26   10.654%   $255.8984   $255.90   $255.90   $255.90  
  Purchase #6 $124.82   12.581%   $140.5236   $140.52   $140.50   $140.50  
  Purchase #7 $148.46   3.217%   $153.236   $153.24   $153.25   $153.20  
  7 purchase totals = $1,144.98       $1,236.7531   $1,236.75   $1,236.75   $1,236.70