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 $213.84   12.772%   $241.1516   $241.15   $241.15   $241.20  
  Purchase #2 $23.90   12.329%   $26.8466   $26.85   $26.85   $26.80  
  Purchase #3 $191.99   9.356%   $209.9526   $209.95   $209.95   $210.00  
  Purchase #4 $152.41   13.840%   $173.5035   $173.50   $173.50   $173.50  
  Purchase #5 $170.32   6.873%   $182.0261   $182.03   $182.05   $182.00  
  Purchase #6 $81.78   9.464%   $89.5197   $89.52   $89.50   $89.50  
  Purchase #7 $218.34   12.654%   $245.9687   $245.97   $245.95   $246.00  
  7 purchase totals = $1,052.58       $1,168.9688   $1,168.97   $1,168.95   $1,169.00