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 $44.74   7.251%   $47.9841   $47.98   $48.00   $48.00  
  Purchase #2 $63.61   7.409%   $68.3229   $68.32   $68.30   $68.30  
  Purchase #3 $65.30   3.315%   $67.4647   $67.46   $67.45   $67.50  
  Purchase #4 $67.63   13.560%   $76.8006   $76.80   $76.80   $76.80  
  Purchase #5 $220.61   5.599%   $232.962   $232.96   $232.95   $233.00  
  Purchase #6 $180.78   6.367%   $192.2903   $192.29   $192.30   $192.30  
  Purchase #7 $190.28   9.461%   $208.2824   $208.28   $208.30   $208.30  
  7 purchase totals = $832.95       $894.1070   $894.09   $894.10   $894.20