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 $58.41   9.767%   $64.1149   $64.11   $64.10   $64.10  
  Purchase #2 $105.27   13.589%   $119.5751   $119.58   $119.60   $119.60  
  Purchase #3 $169.73   4.237%   $176.9215   $176.92   $176.90   $176.90  
  Purchase #4 $137.96   10.616%   $152.6058   $152.61   $152.60   $152.60  
  Purchase #5 $81.74   6.797%   $87.2959   $87.30   $87.30   $87.30  
  Purchase #6 $216.37   3.527%   $224.0014   $224.00   $224.00   $224.00  
  Purchase #7 $201.87   13.726%   $229.5787   $229.58   $229.60   $229.60  
  7 purchase totals = $971.35       $1,054.0933   $1,054.10   $1,054.10   $1,054.10