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 $89.30   5.467%   $94.182   $94.18   $94.20   $94.20  
  Purchase #2 $50.29   5.247%   $52.9287   $52.93   $52.95   $52.90  
  Purchase #3 $115.47   11.104%   $128.2918   $128.29   $128.30   $128.30  
  Purchase #4 $172.86   7.197%   $185.3007   $185.30   $185.30   $185.30  
  Purchase #5 $197.42   8.603%   $214.404   $214.40   $214.40   $214.40  
  Purchase #6 $70.49   3.209%   $72.752   $72.75   $72.75   $72.80  
  Purchase #7 $92.53   5.661%   $97.7681   $97.77   $97.75   $97.80  
  7 purchase totals = $788.36       $845.6273   $845.62   $845.65   $845.70