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 $60.39   7.599%   $64.979   $64.98   $65.00   $65.00  
  Purchase #2 $95.58   9.427%   $104.5903   $104.59   $104.60   $104.60  
  Purchase #3 $100.84   9.766%   $110.688   $110.69   $110.70   $110.70  
  Purchase #4 $238.31   11.387%   $265.4464   $265.45   $265.45   $265.40  
  Purchase #5 $230.70   12.300%   $259.0761   $259.08   $259.10   $259.10  
  Purchase #6 $239.33   12.545%   $269.3539   $269.35   $269.35   $269.40  
  Purchase #7 $151.99   11.728%   $169.8154   $169.82   $169.80   $169.80  
  7 purchase totals = $1,117.14       $1,243.9491   $1,243.96   $1,244.00   $1,244.00