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 $62.57   8.794%   $68.0724   $68.07   $68.05   $68.10  
  Purchase #2 $195.65   12.677%   $220.4526   $220.45   $220.45   $220.50  
  Purchase #3 $186.97   13.561%   $212.325   $212.33   $212.35   $212.30  
  Purchase #4 $88.37   10.636%   $97.769   $97.77   $97.75   $97.80  
  Purchase #5 $193.30   13.721%   $219.8227   $219.82   $219.80   $219.80  
  Purchase #6 $194.62   5.232%   $204.8025   $204.80   $204.80   $204.80  
  Purchase #7 $127.67   7.595%   $137.3665   $137.37   $137.35   $137.40  
  7 purchase totals = $1,049.15       $1,160.6107   $1,160.61   $1,160.55   $1,160.70