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 $106.58   9.552%   $116.7605   $116.76   $116.75   $116.80  
  Purchase #2 $244.83   8.118%   $264.7053   $264.71   $264.70   $264.70  
  Purchase #3 $58.72   13.420%   $66.6002   $66.60   $66.60   $66.60  
  Purchase #4 $41.32   12.282%   $46.3949   $46.39   $46.40   $46.40  
  Purchase #5 $217.31   4.544%   $227.1846   $227.18   $227.20   $227.20  
  Purchase #6 $244.77   8.168%   $264.7628   $264.76   $264.75   $264.80  
  Purchase #7 $187.82   10.229%   $207.0321   $207.03   $207.05   $207.00  
  7 purchase totals = $1,101.35       $1,193.4404   $1,193.43   $1,193.45   $1,193.50