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 $58.75   5.843%   $62.1828   $62.18   $62.20   $62.20  
  Purchase #2 $236.49   6.575%   $252.0392   $252.04   $252.05   $252.00  
  Purchase #3 $204.61   13.397%   $232.0216   $232.02   $232.00   $232.00  
  Purchase #4 $175.81   6.561%   $187.3449   $187.34   $187.35   $187.30  
  Purchase #5 $195.82   7.828%   $211.1488   $211.15   $211.15   $211.10  
  Purchase #6 $238.52   6.451%   $253.9069   $253.91   $253.90   $253.90  
  Purchase #7 $42.75   4.782%   $44.7943   $44.79   $44.80   $44.80  
  7 purchase totals = $1,152.75       $1,243.4385   $1,243.43   $1,243.45   $1,243.30