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 $70.62   4.193%   $73.5811   $73.58   $73.60   $73.60  
  Purchase #2 $210.93   10.569%   $233.2232   $233.22   $233.20   $233.20  
  Purchase #3 $131.92   10.363%   $145.5909   $145.59   $145.60   $145.60  
  Purchase #4 $87.40   13.166%   $98.9071   $98.91   $98.90   $98.90  
  Purchase #5 $211.72   8.795%   $230.3408   $230.34   $230.35   $230.30  
  Purchase #6 $243.74   6.589%   $259.8   $259.80   $259.80   $259.80  
  Purchase #7 $17.60   7.494%   $18.9189   $18.92   $18.90   $18.90  
  7 purchase totals = $973.93       $1,060.3620   $1,060.36   $1,060.35   $1,060.30