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 $184.46   6.203%   $195.9021   $195.90   $195.90   $195.90  
  Purchase #2 $43.46   6.594%   $46.3258   $46.33   $46.35   $46.30  
  Purchase #3 $85.82   9.608%   $94.0656   $94.07   $94.05   $94.10  
  Purchase #4 $49.79   7.836%   $53.6915   $53.69   $53.70   $53.70  
  Purchase #5 $222.33   3.640%   $230.4228   $230.42   $230.40   $230.40  
  Purchase #6 $216.83   3.457%   $224.3258   $224.33   $224.35   $224.30  
  Purchase #7 $195.62   6.228%   $207.8032   $207.80   $207.80   $207.80  
  7 purchase totals = $998.31       $1,052.5368   $1,052.54   $1,052.55   $1,052.50