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 $197.63   13.462%   $224.235   $224.24   $224.25   $224.20  
  Purchase #2 $41.98   3.399%   $43.4069   $43.41   $43.40   $43.40  
  Purchase #3 $223.60   12.683%   $251.9592   $251.96   $251.95   $252.00  
  Purchase #4 $83.58   10.713%   $92.5339   $92.53   $92.55   $92.50  
  Purchase #5 $91.60   8.457%   $99.3466   $99.35   $99.35   $99.30  
  Purchase #6 $192.26   9.671%   $210.8535   $210.85   $210.85   $210.90  
  Purchase #7 $246.43   6.842%   $263.2907   $263.29   $263.30   $263.30  
  7 purchase totals = $1,077.08       $1,185.6258   $1,185.63   $1,185.65   $1,185.60