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 $92.81   9.292%   $101.4339   $101.43   $101.45   $101.40  
  Purchase #2 $202.78   11.131%   $225.3514   $225.35   $225.35   $225.40  
  Purchase #3 $24.81   5.654%   $26.2128   $26.21   $26.20   $26.20  
  Purchase #4 $236.46   12.363%   $265.6935   $265.69   $265.70   $265.70  
  Purchase #5 $211.88   10.324%   $233.7545   $233.75   $233.75   $233.80  
  Purchase #6 $184.26   5.608%   $194.5933   $194.59   $194.60   $194.60  
  Purchase #7 $180.44   12.478%   $202.9553   $202.96   $202.95   $203.00  
  7 purchase totals = $1,133.44       $1,249.9947   $1,249.98   $1,250.00   $1,250.10