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 $168.27   7.676%   $181.1864   $181.19   $181.20   $181.20  
  Purchase #2 $67.86   10.452%   $74.9527   $74.95   $74.95   $75.00  
  Purchase #3 $101.53   5.689%   $107.306   $107.31   $107.30   $107.30  
  Purchase #4 $207.34   6.477%   $220.7694   $220.77   $220.75   $220.80  
  Purchase #5 $14.33   4.348%   $14.9531   $14.95   $14.95   $15.00  
  Purchase #6 $197.67   3.135%   $203.867   $203.87   $203.85   $203.90  
  Purchase #7 $211.25   4.530%   $220.8196   $220.82   $220.80   $220.80  
  7 purchase totals = $968.25       $1,023.8542   $1,023.86   $1,023.80   $1,024.00