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 $195.53   4.467%   $204.2643   $204.26   $204.25   $204.30  
  Purchase #2 $82.33   7.787%   $88.741   $88.74   $88.75   $88.70  
  Purchase #3 $233.77   7.448%   $251.1812   $251.18   $251.20   $251.20  
  Purchase #4 $200.82   6.548%   $213.9697   $213.97   $213.95   $214.00  
  Purchase #5 $129.98   4.632%   $136.0007   $136.00   $136.00   $136.00  
  Purchase #6 $57.25   5.704%   $60.5155   $60.52   $60.50   $60.50  
  Purchase #7 $112.74   4.168%   $117.439   $117.44   $117.45   $117.40  
  7 purchase totals = $1,012.42       $1,072.1114   $1,072.11   $1,072.10   $1,072.10