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 $82.48   13.394%   $93.5274   $93.53   $93.55   $93.50  
  Purchase #2 $115.48   7.201%   $123.7957   $123.80   $123.80   $123.80  
  Purchase #3 $8.47   3.104%   $8.7329   $8.73   $8.75   $8.70  
  Purchase #4 $126.42   3.171%   $130.4288   $130.43   $130.45   $130.40  
  Purchase #5 $178.84   12.845%   $201.812   $201.81   $201.80   $201.80  
  Purchase #6 $212.96   11.194%   $236.7987   $236.80   $236.80   $236.80  
  Purchase #7 $244.41   12.791%   $275.6725   $275.67   $275.65   $275.70  
  7 purchase totals = $969.06       $1,070.7680   $1,070.77   $1,070.80   $1,070.70