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 $152.49   7.216%   $163.4937   $163.49   $163.50   $163.50  
  Purchase #2 $156.68   7.118%   $167.8325   $167.83   $167.85   $167.80  
  Purchase #3 $243.85   11.229%   $271.2319   $271.23   $271.25   $271.20  
  Purchase #4 $132.71   13.696%   $150.886   $150.89   $150.90   $150.90  
  Purchase #5 $87.59   8.186%   $94.7601   $94.76   $94.75   $94.80  
  Purchase #6 $235.68   8.154%   $254.8973   $254.90   $254.90   $254.90  
  Purchase #7 $85.86   8.467%   $93.1298   $93.13   $93.15   $93.10  
  7 purchase totals = $1,094.86       $1,196.2313   $1,196.23   $1,196.30   $1,196.20