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 $67.48   6.315%   $71.7414   $71.74   $71.75   $71.70  
  Purchase #2 $24.36   6.644%   $25.9785   $25.98   $26.00   $26.00  
  Purchase #3 $200.55   4.598%   $209.7713   $209.77   $209.75   $209.80  
  Purchase #4 $239.52   12.747%   $270.0516   $270.05   $270.05   $270.10  
  Purchase #5 $221.85   10.767%   $245.7366   $245.74   $245.75   $245.70  
  Purchase #6 $228.84   11.853%   $255.9644   $255.96   $255.95   $256.00  
  Purchase #7 $169.37   7.355%   $181.8272   $181.83   $181.85   $181.80  
  7 purchase totals = $1,151.97       $1,261.0710   $1,261.07   $1,261.10   $1,261.10