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 $92.62   4.417%   $96.711   $96.71   $96.70   $96.70  
  Purchase #2 $34.94   3.344%   $36.1084   $36.11   $36.10   $36.10  
  Purchase #3 $188.74   12.241%   $211.8437   $211.84   $211.85   $211.80  
  Purchase #4 $248.39   7.775%   $267.7023   $267.70   $267.70   $267.70  
  Purchase #5 $142.75   13.291%   $161.7229   $161.72   $161.70   $161.70  
  Purchase #6 $212.94   12.145%   $238.8016   $238.80   $238.80   $238.80  
  Purchase #7 $148.28   9.838%   $162.8678   $162.87   $162.85   $162.90  
  7 purchase totals = $1,068.66       $1,175.7577   $1,175.75   $1,175.70   $1,175.70