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 $132.96   9.809%   $146.002   $146.00   $146.00   $146.00  
  Purchase #2 $90.65   13.140%   $102.5614   $102.56   $102.55   $102.60  
  Purchase #3 $107.39   6.763%   $114.6528   $114.65   $114.65   $114.70  
  Purchase #4 $101.92   10.651%   $112.7755   $112.78   $112.80   $112.80  
  Purchase #5 $151.36   9.823%   $166.2281   $166.23   $166.25   $166.20  
  Purchase #6 $177.87   12.281%   $199.7142   $199.71   $199.70   $199.70  
  Purchase #7 $219.55   6.388%   $233.5749   $233.57   $233.55   $233.60  
  7 purchase totals = $981.70       $1,075.5089   $1,075.50   $1,075.50   $1,075.60