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 $55.26   10.776%   $61.2148   $61.21   $61.20   $61.20  
  Purchase #2 $120.71   4.576%   $126.2337   $126.23   $126.25   $126.20  
  Purchase #3 $160.50   4.271%   $167.355   $167.36   $167.35   $167.40  
  Purchase #4 $118.25   11.644%   $132.019   $132.02   $132.00   $132.00  
  Purchase #5 $245.56   9.519%   $268.9349   $268.93   $268.95   $268.90  
  Purchase #6 $111.70   12.535%   $125.7016   $125.70   $125.70   $125.70  
  Purchase #7 $126.28   5.324%   $133.0031   $133.00   $133.00   $133.00  
  7 purchase totals = $938.26       $1,014.4621   $1,014.45   $1,014.45   $1,014.40