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 $214.93   9.323%   $234.9679   $234.97   $234.95   $235.00  
  Purchase #2 $213.36   13.217%   $241.5598   $241.56   $241.55   $241.60  
  Purchase #3 $235.80   3.572%   $244.2228   $244.22   $244.20   $244.20  
  Purchase #4 $75.76   9.540%   $82.9875   $82.99   $83.00   $83.00  
  Purchase #5 $210.74   12.288%   $236.6357   $236.64   $236.65   $236.60  
  Purchase #6 $54.86   4.653%   $57.4126   $57.41   $57.40   $57.40  
  Purchase #7 $227.58   7.169%   $243.8952   $243.90   $243.90   $243.90  
  7 purchase totals = $1,233.03       $1,341.6815   $1,341.69   $1,341.65   $1,341.70