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 $53.75   13.515%   $61.0143   $61.01   $61.00   $61.00  
  Purchase #2 $168.30   9.390%   $184.1034   $184.10   $184.10   $184.10  
  Purchase #3 $5.64   10.600%   $6.2378   $6.24   $6.25   $6.20  
  Purchase #4 $210.62   10.768%   $233.2996   $233.30   $233.30   $233.30  
  Purchase #5 $176.96   11.594%   $197.4767   $197.48   $197.50   $197.50  
  Purchase #6 $84.84   5.131%   $89.1931   $89.19   $89.20   $89.20  
  Purchase #7 $117.62   12.783%   $132.6554   $132.66   $132.65   $132.70  
  7 purchase totals = $817.73       $903.9803   $903.98   $904.00   $904.00