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 $89.50   10.570%   $98.9602   $98.96   $98.95   $99.00  
  Purchase #2 $152.84   10.539%   $168.9478   $168.95   $168.95   $168.90  
  Purchase #3 $202.36   4.366%   $211.195   $211.20   $211.20   $211.20  
  Purchase #4 $249.31   4.185%   $259.7436   $259.74   $259.75   $259.70  
  Purchase #5 $32.96   11.483%   $36.7448   $36.74   $36.75   $36.70  
  Purchase #6 $209.57   3.154%   $216.1798   $216.18   $216.20   $216.20  
  Purchase #7 $187.51   12.469%   $210.8906   $210.89   $210.90   $210.90  
  7 purchase totals = $1,124.05       $1,202.6618   $1,202.66   $1,202.70   $1,202.60