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 $211.76   6.495%   $225.5138   $225.51   $225.50   $225.50  
  Purchase #2 $185.76   7.306%   $199.3316   $199.33   $199.35   $199.30  
  Purchase #3 $22.35   9.716%   $24.5215   $24.52   $24.50   $24.50  
  Purchase #4 $127.68   4.850%   $133.8725   $133.87   $133.85   $133.90  
  Purchase #5 $231.90   6.753%   $247.5602   $247.56   $247.55   $247.60  
  Purchase #6 $60.55   5.141%   $63.6629   $63.66   $63.65   $63.70  
  Purchase #7 $229.75   12.114%   $257.5819   $257.58   $257.60   $257.60  
  7 purchase totals = $1,069.75       $1,152.0444   $1,152.03   $1,152.00   $1,152.10