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 $60.33   3.340%   $62.345   $62.35   $62.35   $62.30  
  Purchase #2 $120.96   12.308%   $135.8478   $135.85   $135.85   $135.80  
  Purchase #3 $215.96   12.182%   $242.2682   $242.27   $242.25   $242.30  
  Purchase #4 $138.86   7.872%   $149.7911   $149.79   $149.80   $149.80  
  Purchase #5 $114.57   9.512%   $125.4679   $125.47   $125.45   $125.50  
  Purchase #6 $238.82   9.153%   $260.6792   $260.68   $260.70   $260.70  
  Purchase #7 $191.78   8.324%   $207.7438   $207.74   $207.75   $207.70  
  7 purchase totals = $1,081.28       $1,184.1430   $1,184.15   $1,184.15   $1,184.10