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 $47.41   13.874%   $53.9877   $53.99   $54.00   $54.00  
  Purchase #2 $148.60   6.124%   $157.7003   $157.70   $157.70   $157.70  
  Purchase #3 $154.80   9.391%   $169.3373   $169.34   $169.35   $169.30  
  Purchase #4 $232.53   5.543%   $245.4191   $245.42   $245.40   $245.40  
  Purchase #5 $145.78   9.200%   $159.1918   $159.19   $159.20   $159.20  
  Purchase #6 $199.92   5.606%   $211.1275   $211.13   $211.15   $211.10  
  Purchase #7 $108.63   10.282%   $119.7993   $119.80   $119.80   $119.80  
  7 purchase totals = $1,037.67       $1,116.5630   $1,116.57   $1,116.60   $1,116.50