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 $85.48   10.767%   $94.6836   $94.68   $94.70   $94.70  
  Purchase #2 $150.58   13.343%   $170.6719   $170.67   $170.65   $170.70  
  Purchase #3 $144.78   7.167%   $155.1564   $155.16   $155.15   $155.20  
  Purchase #4 $221.47   10.838%   $245.4729   $245.47   $245.45   $245.50  
  Purchase #5 $148.54   5.589%   $156.8419   $156.84   $156.85   $156.80  
  Purchase #6 $128.83   9.776%   $141.4244   $141.42   $141.40   $141.40  
  Purchase #7 $218.52   5.743%   $231.0696   $231.07   $231.05   $231.10  
  7 purchase totals = $1,098.20       $1,195.3207   $1,195.31   $1,195.25   $1,195.40