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 $62.62   9.864%   $68.7968   $68.80   $68.80   $68.80  
  Purchase #2 $231.25   4.376%   $241.3695   $241.37   $241.35   $241.40  
  Purchase #3 $247.82   3.216%   $255.7899   $255.79   $255.80   $255.80  
  Purchase #4 $72.86   3.267%   $75.2403   $75.24   $75.25   $75.20  
  Purchase #5 $238.29   11.492%   $265.6743   $265.67   $265.65   $265.70  
  Purchase #6 $235.53   4.162%   $245.3328   $245.33   $245.35   $245.30  
  Purchase #7 $88.95   6.754%   $94.9577   $94.96   $94.95   $95.00  
  7 purchase totals = $1,177.32       $1,247.1613   $1,247.16   $1,247.15   $1,247.20