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 $148.43   8.457%   $160.9827   $160.98   $161.00   $161.00  
  Purchase #2 $180.83   8.142%   $195.5532   $195.55   $195.55   $195.60  
  Purchase #3 $145.55   5.703%   $153.8507   $153.85   $153.85   $153.90  
  Purchase #4 $231.35   13.522%   $262.6331   $262.63   $262.65   $262.60  
  Purchase #5 $43.59   11.702%   $48.6909   $48.69   $48.70   $48.70  
  Purchase #6 $62.41   10.207%   $68.7802   $68.78   $68.80   $68.80  
  Purchase #7 $54.89   4.595%   $57.4122   $57.41   $57.40   $57.40  
  7 purchase totals = $867.05       $947.9030   $947.89   $947.95   $948.00