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 $175.88   8.370%   $190.6012   $190.60   $190.60   $190.60  
  Purchase #2 $57.80   12.440%   $64.9903   $64.99   $65.00   $65.00  
  Purchase #3 $95.57   10.155%   $105.2751   $105.28   $105.30   $105.30  
  Purchase #4 $124.78   4.661%   $130.596   $130.60   $130.60   $130.60  
  Purchase #5 $209.42   11.255%   $232.9902   $232.99   $233.00   $233.00  
  Purchase #6 $73.88   13.753%   $84.0407   $84.04   $84.05   $84.00  
  Purchase #7 $70.28   10.323%   $77.535   $77.54   $77.55   $77.50  
  7 purchase totals = $807.61       $886.0285   $886.04   $886.10   $886.00