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 $235.28   4.834%   $246.6534   $246.65   $246.65   $246.70  
  Purchase #2 $48.98   11.809%   $54.764   $54.76   $54.75   $54.80  
  Purchase #3 $107.81   5.370%   $113.5994   $113.60   $113.60   $113.60  
  Purchase #4 $152.38   9.342%   $166.6153   $166.62   $166.60   $166.60  
  Purchase #5 $147.38   9.322%   $161.1188   $161.12   $161.10   $161.10  
  Purchase #6 $233.96   4.518%   $244.5303   $244.53   $244.55   $244.50  
  Purchase #7 $185.30   6.721%   $197.754   $197.75   $197.75   $197.80  
  7 purchase totals = $1,111.09       $1,185.0352   $1,185.03   $1,185.00   $1,185.10