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 $215.41   10.279%   $237.552   $237.55   $237.55   $237.60  
  Purchase #2 $95.47   4.328%   $99.6019   $99.60   $99.60   $99.60  
  Purchase #3 $127.59   11.310%   $142.0204   $142.02   $142.00   $142.00  
  Purchase #4 $162.86   8.781%   $177.1607   $177.16   $177.15   $177.20  
  Purchase #5 $217.78   5.244%   $229.2004   $229.20   $229.20   $229.20  
  Purchase #6 $40.61   10.700%   $44.9553   $44.96   $44.95   $45.00  
  Purchase #7 $210.69   5.251%   $221.7533   $221.75   $221.75   $221.80  
  7 purchase totals = $1,070.41       $1,152.2440   $1,152.24   $1,152.20   $1,152.40