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 $114.74   7.163%   $122.9588   $122.96   $122.95   $123.00  
  Purchase #2 $148.54   4.728%   $155.563   $155.56   $155.55   $155.60  
  Purchase #3 $120.69   4.317%   $125.9002   $125.90   $125.90   $125.90  
  Purchase #4 $25.89   5.821%   $27.3971   $27.40   $27.40   $27.40  
  Purchase #5 $229.82   6.799%   $245.4455   $245.45   $245.45   $245.40  
  Purchase #6 $117.74   4.614%   $123.1725   $123.17   $123.15   $123.20  
  Purchase #7 $194.90   8.761%   $211.9752   $211.98   $212.00   $212.00  
  7 purchase totals = $952.32       $1,012.4123   $1,012.42   $1,012.40   $1,012.50