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 $41.27   11.143%   $45.8687   $45.87   $45.85   $45.90  
  Purchase #2 $86.53   11.815%   $96.7535   $96.75   $96.75   $96.80  
  Purchase #3 $94.62   8.120%   $102.3031   $102.30   $102.30   $102.30  
  Purchase #4 $205.66   10.840%   $227.9535   $227.95   $227.95   $228.00  
  Purchase #5 $122.58   11.446%   $136.6105   $136.61   $136.60   $136.60  
  Purchase #6 $191.65   8.165%   $207.2982   $207.30   $207.30   $207.30  
  Purchase #7 $185.95   6.315%   $197.6927   $197.69   $197.70   $197.70  
  7 purchase totals = $928.26       $1,014.4802   $1,014.47   $1,014.45   $1,014.60