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 $86.71   7.596%   $93.2965   $93.30   $93.30   $93.30  
  Purchase #2 $93.31   9.568%   $102.2379   $102.24   $102.25   $102.20  
  Purchase #3 $201.37   11.244%   $224.012   $224.01   $224.00   $224.00  
  Purchase #4 $190.69   6.525%   $203.1325   $203.13   $203.15   $203.10  
  Purchase #5 $46.79   4.414%   $48.8553   $48.86   $48.85   $48.90  
  Purchase #6 $213.58   11.481%   $238.1011   $238.10   $238.10   $238.10  
  Purchase #7 $229.89   5.594%   $242.75   $242.75   $242.75   $242.80  
  7 purchase totals = $1,062.34       $1,152.3853   $1,152.39   $1,152.40   $1,152.40