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 $89.96   6.345%   $95.668   $95.67   $95.65   $95.70  
  Purchase #2 $137.26   7.422%   $147.4474   $147.45   $147.45   $147.40  
  Purchase #3 $202.35   9.791%   $222.1621   $222.16   $222.15   $222.20  
  Purchase #4 $62.47   3.659%   $64.7558   $64.76   $64.75   $64.80  
  Purchase #5 $247.74   3.279%   $255.8634   $255.86   $255.85   $255.90  
  Purchase #6 $185.73   12.419%   $208.7958   $208.80   $208.80   $208.80  
  Purchase #7 $200.50   4.406%   $209.334   $209.33   $209.35   $209.30  
  7 purchase totals = $1,126.01       $1,204.0265   $1,204.03   $1,204.00   $1,204.10