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 $56.42   7.526%   $60.6662   $60.67   $60.65   $60.70  
  Purchase #2 $189.80   3.425%   $196.3007   $196.30   $196.30   $196.30  
  Purchase #3 $221.71   11.513%   $247.2355   $247.24   $247.25   $247.20  
  Purchase #4 $159.44   9.211%   $174.126   $174.13   $174.15   $174.10  
  Purchase #5 $204.35   12.573%   $230.0429   $230.04   $230.05   $230.00  
  Purchase #6 $59.89   8.790%   $65.1543   $65.15   $65.15   $65.20  
  Purchase #7 $187.45   13.188%   $212.1709   $212.17   $212.15   $212.20  
  7 purchase totals = $1,079.06       $1,185.6965   $1,185.70   $1,185.70   $1,185.70