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 $86.32   10.580%   $95.4527   $95.45   $95.45   $95.50  
  Purchase #2 $62.43   4.642%   $65.328   $65.33   $65.35   $65.30  
  Purchase #3 $46.29   4.830%   $48.5258   $48.53   $48.55   $48.50  
  Purchase #4 $223.50   10.214%   $246.3283   $246.33   $246.35   $246.30  
  Purchase #5 $132.95   8.308%   $143.9955   $144.00   $144.00   $144.00  
  Purchase #6 $250.91   9.198%   $273.9887   $273.99   $274.00   $274.00  
  Purchase #7 $177.47   5.408%   $187.0676   $187.07   $187.05   $187.10  
  7 purchase totals = $979.87       $1,060.6866   $1,060.70   $1,060.75   $1,060.70