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 $61.48   11.567%   $68.5914   $68.59   $68.60   $68.60  
  Purchase #2 $122.53   3.401%   $126.6972   $126.70   $126.70   $126.70  
  Purchase #3 $167.88   4.175%   $174.889   $174.89   $174.90   $174.90  
  Purchase #4 $89.33   4.693%   $93.5223   $93.52   $93.50   $93.50  
  Purchase #5 $7.42   8.146%   $8.0244   $8.02   $8.00   $8.00  
  Purchase #6 $227.93   12.159%   $255.644   $255.64   $255.65   $255.60  
  Purchase #7 $184.64   5.466%   $194.7324   $194.73   $194.75   $194.70  
  7 purchase totals = $861.21       $922.1007   $922.09   $922.10   $922.00