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 $184.34   9.744%   $202.3021   $202.30   $202.30   $202.30  
  Purchase #2 $165.61   10.667%   $183.2756   $183.28   $183.30   $183.30  
  Purchase #3 $119.64   5.150%   $125.8015   $125.80   $125.80   $125.80  
  Purchase #4 $48.68   7.694%   $52.4254   $52.43   $52.45   $52.40  
  Purchase #5 $217.28   6.134%   $230.608   $230.61   $230.60   $230.60  
  Purchase #6 $112.86   4.402%   $117.8281   $117.83   $117.85   $117.80  
  Purchase #7 $219.62   4.204%   $228.8528   $228.85   $228.85   $228.90  
  7 purchase totals = $1,068.03       $1,141.0935   $1,141.10   $1,141.15   $1,141.10