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 $56.52   9.752%   $62.0318   $62.03   $62.05   $62.00  
  Purchase #2 $200.44   6.179%   $212.8252   $212.83   $212.85   $212.80  
  Purchase #3 $42.55   6.232%   $45.2017   $45.20   $45.20   $45.20  
  Purchase #4 $227.75   13.208%   $257.8312   $257.83   $257.85   $257.80  
  Purchase #5 $159.37   9.818%   $175.0169   $175.02   $175.00   $175.00  
  Purchase #6 $109.37   8.775%   $118.9672   $118.97   $118.95   $119.00  
  Purchase #7 $20.52   7.340%   $22.0262   $22.03   $22.05   $22.00  
  7 purchase totals = $816.52       $893.9002   $893.91   $893.95   $893.80