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 $198.56   5.859%   $210.1936   $210.19   $210.20   $210.20  
  Purchase #2 $177.54   9.659%   $194.6886   $194.69   $194.70   $194.70  
  Purchase #3 $218.33   7.680%   $235.0977   $235.10   $235.10   $235.10  
  Purchase #4 $194.85   8.182%   $210.7926   $210.79   $210.80   $210.80  
  Purchase #5 $177.89   6.793%   $189.9741   $189.97   $189.95   $190.00  
  Purchase #6 $143.47   5.445%   $151.2819   $151.28   $151.30   $151.30  
  Purchase #7 $228.81   6.802%   $244.3737   $244.37   $244.35   $244.40  
  7 purchase totals = $1,339.45       $1,436.4022   $1,436.39   $1,436.40   $1,436.50