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 $55.43   10.199%   $61.0833   $61.08   $61.10   $61.10  
  Purchase #2 $74.66   5.745%   $78.9492   $78.95   $78.95   $78.90  
  Purchase #3 $147.50   9.809%   $161.9683   $161.97   $161.95   $162.00  
  Purchase #4 $144.42   10.332%   $159.3415   $159.34   $159.35   $159.30  
  Purchase #5 $126.99   13.396%   $144.0016   $144.00   $144.00   $144.00  
  Purchase #6 $184.98   11.672%   $206.5709   $206.57   $206.55   $206.60  
  Purchase #7 $208.25   11.600%   $232.407   $232.41   $232.40   $232.40  
  7 purchase totals = $942.23       $1,044.3218   $1,044.32   $1,044.30   $1,044.30