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 $44.46   8.413%   $48.2004   $48.20   $48.20   $48.20  
  Purchase #2 $155.57   10.503%   $171.9095   $171.91   $171.90   $171.90  
  Purchase #3 $146.78   5.673%   $155.1068   $155.11   $155.10   $155.10  
  Purchase #4 $201.28   9.667%   $220.7377   $220.74   $220.75   $220.70  
  Purchase #5 $166.79   6.519%   $177.663   $177.66   $177.65   $177.70  
  Purchase #6 $132.55   11.820%   $148.2174   $148.22   $148.20   $148.20  
  Purchase #7 $172.83   4.159%   $180.018   $180.02   $180.00   $180.00  
  7 purchase totals = $1,020.26       $1,101.8528   $1,101.86   $1,101.80   $1,101.80