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 $88.80   7.519%   $95.4769   $95.48   $95.50   $95.50  
  Purchase #2 $8.83   11.561%   $9.8508   $9.85   $9.85   $9.90  
  Purchase #3 $228.61   6.494%   $243.4559   $243.46   $243.45   $243.50  
  Purchase #4 $32.78   10.487%   $36.2176   $36.22   $36.20   $36.20  
  Purchase #5 $198.81   11.541%   $221.7547   $221.75   $221.75   $221.80  
  Purchase #6 $173.68   11.355%   $193.4014   $193.40   $193.40   $193.40  
  Purchase #7 $231.54   13.854%   $263.6176   $263.62   $263.60   $263.60  
  7 purchase totals = $963.05       $1,063.7749   $1,063.78   $1,063.75   $1,063.90