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 $141.27   8.506%   $153.2864   $153.29   $153.30   $153.30  
  Purchase #2 $208.92   13.442%   $237.003   $237.00   $237.00   $237.00  
  Purchase #3 $160.37   11.512%   $178.8318   $178.83   $178.85   $178.80  
  Purchase #4 $86.75   11.808%   $96.9934   $96.99   $97.00   $97.00  
  Purchase #5 $195.36   3.548%   $202.2914   $202.29   $202.30   $202.30  
  Purchase #6 $124.97   11.814%   $139.734   $139.73   $139.75   $139.70  
  Purchase #7 $36.52   11.802%   $40.8301   $40.83   $40.85   $40.80  
  7 purchase totals = $954.16       $1,048.9701   $1,048.96   $1,049.05   $1,048.90