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 $168.58   3.347%   $174.2224   $174.22   $174.20   $174.20  
  Purchase #2 $212.91   9.282%   $232.6723   $232.67   $232.65   $232.70  
  Purchase #3 $215.79   10.364%   $238.1545   $238.15   $238.15   $238.20  
  Purchase #4 $44.42   11.648%   $49.594   $49.59   $49.60   $49.60  
  Purchase #5 $244.96   9.547%   $268.3463   $268.35   $268.35   $268.30  
  Purchase #6 $58.99   5.579%   $62.2811   $62.28   $62.30   $62.30  
  Purchase #7 $117.86   11.852%   $131.8288   $131.83   $131.85   $131.80  
  7 purchase totals = $1,063.51       $1,157.0994   $1,157.09   $1,157.10   $1,157.10