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 $194.84   5.454%   $205.4666   $205.47   $205.45   $205.50  
  Purchase #2 $118.84   11.508%   $132.5161   $132.52   $132.50   $132.50  
  Purchase #3 $73.35   6.310%   $77.9784   $77.98   $78.00   $78.00  
  Purchase #4 $82.41   13.860%   $93.832   $93.83   $93.85   $93.80  
  Purchase #5 $238.84   12.280%   $268.1696   $268.17   $268.15   $268.20  
  Purchase #6 $119.66   13.748%   $136.1109   $136.11   $136.10   $136.10  
  Purchase #7 $108.75   9.202%   $118.7572   $118.76   $118.75   $118.80  
  7 purchase totals = $936.69       $1,032.8308   $1,032.84   $1,032.80   $1,032.90