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 $164.35   11.511%   $183.2683   $183.27   $183.25   $183.30  
  Purchase #2 $195.90   4.294%   $204.3119   $204.31   $204.30   $204.30  
  Purchase #3 $198.80   10.180%   $219.0378   $219.04   $219.05   $219.00  
  Purchase #4 $96.66   3.757%   $100.2915   $100.29   $100.30   $100.30  
  Purchase #5 $206.84   8.410%   $224.2352   $224.24   $224.25   $224.20  
  Purchase #6 $47.82   11.377%   $53.2605   $53.26   $53.25   $53.30  
  Purchase #7 $154.44   10.180%   $170.162   $170.16   $170.15   $170.20  
  7 purchase totals = $1,064.81       $1,154.5672   $1,154.57   $1,154.55   $1,154.60