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 $147.35   10.251%   $162.4548   $162.45   $162.45   $162.50  
  Purchase #2 $232.62   11.140%   $258.5339   $258.53   $258.55   $258.50  
  Purchase #3 $89.96   13.217%   $101.85   $101.85   $101.85   $101.90  
  Purchase #4 $43.48   5.605%   $45.9171   $45.92   $45.90   $45.90  
  Purchase #5 $84.39   11.723%   $94.283   $94.28   $94.30   $94.30  
  Purchase #6 $237.45   6.435%   $252.7299   $252.73   $252.75   $252.70  
  Purchase #7 $220.64   7.758%   $237.7573   $237.76   $237.75   $237.80  
  7 purchase totals = $1,055.89       $1,153.5260   $1,153.52   $1,153.55   $1,153.60