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 $214.98   8.846%   $233.9971   $234.00   $234.00   $234.00  
  Purchase #2 $199.59   9.417%   $218.3854   $218.39   $218.40   $218.40  
  Purchase #3 $245.50   13.108%   $277.6801   $277.68   $277.70   $277.70  
  Purchase #4 $194.64   12.855%   $219.661   $219.66   $219.65   $219.70  
  Purchase #5 $118.96   6.593%   $126.803   $126.80   $126.80   $126.80  
  Purchase #6 $177.65   8.104%   $192.0468   $192.05   $192.05   $192.00  
  Purchase #7 $222.26   10.809%   $246.2841   $246.28   $246.30   $246.30  
  7 purchase totals = $1,373.58       $1,514.8575   $1,514.86   $1,514.90   $1,514.90