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 $194.93   9.613%   $213.6686   $213.67   $213.65   $213.70  
  Purchase #2 $211.26   6.647%   $225.3025   $225.30   $225.30   $225.30  
  Purchase #3 $159.97   4.266%   $166.7943   $166.79   $166.80   $166.80  
  Purchase #4 $245.80   9.682%   $269.5984   $269.60   $269.60   $269.60  
  Purchase #5 $184.91   5.541%   $195.1559   $195.16   $195.15   $195.20  
  Purchase #6 $50.84   4.547%   $53.1517   $53.15   $53.15   $53.20  
  Purchase #7 $36.56   5.829%   $38.6911   $38.69   $38.70   $38.70  
  7 purchase totals = $1,084.27       $1,162.3625   $1,162.36   $1,162.35   $1,162.50