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 $169.82   13.472%   $192.6982   $192.70   $192.70   $192.70  
  Purchase #2 $187.34   8.289%   $202.8686   $202.87   $202.85   $202.90  
  Purchase #3 $96.29   12.254%   $108.0894   $108.09   $108.10   $108.10  
  Purchase #4 $250.35   8.861%   $272.5335   $272.53   $272.55   $272.50  
  Purchase #5 $32.29   6.420%   $34.363   $34.36   $34.35   $34.40  
  Purchase #6 $116.68   9.429%   $127.6818   $127.68   $127.70   $127.70  
  Purchase #7 $118.67   6.152%   $125.9706   $125.97   $125.95   $126.00  
  7 purchase totals = $971.44       $1,064.2051   $1,064.20   $1,064.20   $1,064.30