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 $46.83   4.568%   $48.9692   $48.97   $48.95   $49.00  
  Purchase #2 $194.69   8.586%   $211.4061   $211.41   $211.40   $211.40  
  Purchase #3 $52.75   8.614%   $57.2939   $57.29   $57.30   $57.30  
  Purchase #4 $151.79   13.734%   $172.6368   $172.64   $172.65   $172.60  
  Purchase #5 $39.91   4.674%   $41.7754   $41.78   $41.80   $41.80  
  Purchase #6 $218.41   11.774%   $244.1256   $244.13   $244.15   $244.10  
  Purchase #7 $226.56   8.629%   $246.1099   $246.11   $246.10   $246.10  
  7 purchase totals = $930.94       $1,022.3169   $1,022.33   $1,022.35   $1,022.30