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 $62.52   8.326%   $67.7254   $67.73   $67.75   $67.70  
  Purchase #2 $196.62   3.139%   $202.7919   $202.79   $202.80   $202.80  
  Purchase #3 $44.57   13.855%   $50.7452   $50.75   $50.75   $50.70  
  Purchase #4 $245.79   5.801%   $260.0483   $260.05   $260.05   $260.00  
  Purchase #5 $209.90   8.230%   $227.1748   $227.17   $227.15   $227.20  
  Purchase #6 $202.30   13.130%   $228.862   $228.86   $228.85   $228.90  
  Purchase #7 $152.25   9.741%   $167.0807   $167.08   $167.10   $167.10  
  7 purchase totals = $1,113.95       $1,204.4283   $1,204.43   $1,204.45   $1,204.40