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 $38.40   8.737%   $41.755   $41.76   $41.75   $41.80  
  Purchase #2 $183.65   5.639%   $194.006   $194.01   $194.00   $194.00  
  Purchase #3 $178.49   6.265%   $189.6724   $189.67   $189.65   $189.70  
  Purchase #4 $241.28   4.122%   $251.2256   $251.23   $251.25   $251.20  
  Purchase #5 $122.95   3.261%   $126.9594   $126.96   $126.95   $127.00  
  Purchase #6 $112.25   4.694%   $117.519   $117.52   $117.50   $117.50  
  Purchase #7 $233.35   5.841%   $246.98   $246.98   $247.00   $247.00  
  7 purchase totals = $1,110.37       $1,168.1174   $1,168.13   $1,168.10   $1,168.20