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 $236.60   7.368%   $254.0327   $254.03   $254.05   $254.00  
  Purchase #2 $119.30   3.654%   $123.6592   $123.66   $123.65   $123.70  
  Purchase #3 $193.63   8.825%   $210.7178   $210.72   $210.70   $210.70  
  Purchase #4 $33.77   10.251%   $37.2318   $37.23   $37.25   $37.20  
  Purchase #5 $183.98   11.319%   $204.8047   $204.80   $204.80   $204.80  
  Purchase #6 $157.40   11.394%   $175.3342   $175.33   $175.35   $175.30  
  Purchase #7 $173.59   9.318%   $189.7651   $189.77   $189.75   $189.80  
  7 purchase totals = $1,098.27       $1,195.5455   $1,195.54   $1,195.55   $1,195.50