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 $60.63   3.663%   $62.8509   $62.85   $62.85   $62.90  
  Purchase #2 $91.40   6.459%   $97.3035   $97.30   $97.30   $97.30  
  Purchase #3 $57.47   8.414%   $62.3055   $62.31   $62.30   $62.30  
  Purchase #4 $164.93   7.772%   $177.7484   $177.75   $177.75   $177.70  
  Purchase #5 $213.99   3.301%   $221.0538   $221.05   $221.05   $221.10  
  Purchase #6 $178.97   9.415%   $195.82   $195.82   $195.80   $195.80  
  Purchase #7 $188.35   11.276%   $209.5883   $209.59   $209.60   $209.60  
  7 purchase totals = $955.74       $1,026.6704   $1,026.67   $1,026.65   $1,026.70