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 $163.44   5.751%   $172.8394   $172.84   $172.85   $172.80  
  Purchase #2 $148.51   10.376%   $163.9194   $163.92   $163.90   $163.90  
  Purchase #3 $119.94   5.572%   $126.6231   $126.62   $126.60   $126.60  
  Purchase #4 $102.71   11.714%   $114.7414   $114.74   $114.75   $114.70  
  Purchase #5 $96.43   5.381%   $101.6189   $101.62   $101.60   $101.60  
  Purchase #6 $246.32   9.361%   $269.378   $269.38   $269.40   $269.40  
  Purchase #7 $235.53   4.593%   $246.3479   $246.35   $246.35   $246.30  
  7 purchase totals = $1,112.88       $1,195.4681   $1,195.47   $1,195.45   $1,195.30