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 $84.58   12.589%   $95.2278   $95.23   $95.25   $95.20  
  Purchase #2 $197.56   13.205%   $223.6478   $223.65   $223.65   $223.60  
  Purchase #3 $84.46   3.114%   $87.0901   $87.09   $87.10   $87.10  
  Purchase #4 $26.62   8.385%   $28.8521   $28.85   $28.85   $28.90  
  Purchase #5 $152.86   13.612%   $173.6673   $173.67   $173.65   $173.70  
  Purchase #6 $24.72   4.839%   $25.9162   $25.92   $25.90   $25.90  
  Purchase #7 $38.51   7.401%   $41.3601   $41.36   $41.35   $41.40  
  7 purchase totals = $609.31       $675.7614   $675.77   $675.75   $675.80