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 $88.55   4.612%   $92.6339   $92.63   $92.65   $92.60  
  Purchase #2 $192.70   10.475%   $212.8853   $212.89   $212.90   $212.90  
  Purchase #3 $229.25   12.407%   $257.693   $257.69   $257.70   $257.70  
  Purchase #4 $180.52   12.224%   $202.5868   $202.59   $202.60   $202.60  
  Purchase #5 $41.84   7.312%   $44.8993   $44.90   $44.90   $44.90  
  Purchase #6 $233.88   5.400%   $246.5095   $246.51   $246.50   $246.50  
  Purchase #7 $94.52   6.833%   $100.9786   $100.98   $101.00   $101.00  
  7 purchase totals = $1,061.26       $1,158.1864   $1,158.19   $1,158.25   $1,158.20