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 $228.52   11.433%   $254.6467   $254.65   $254.65   $254.60  
  Purchase #2 $205.69   4.837%   $215.6392   $215.64   $215.65   $215.60  
  Purchase #3 $199.88   9.606%   $219.0805   $219.08   $219.10   $219.10  
  Purchase #4 $73.34   10.853%   $81.2996   $81.30   $81.30   $81.30  
  Purchase #5 $59.58   7.662%   $64.145   $64.15   $64.15   $64.10  
  Purchase #6 $8.71   10.446%   $9.6198   $9.62   $9.60   $9.60  
  Purchase #7 $235.80   12.795%   $265.9706   $265.97   $265.95   $266.00  
  7 purchase totals = $1,011.52       $1,110.4014   $1,110.41   $1,110.40   $1,110.30