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 $192.48   9.690%   $211.1313   $211.13   $211.15   $211.10  
  Purchase #2 $227.78   7.811%   $245.5719   $245.57   $245.55   $245.60  
  Purchase #3 $229.51   3.788%   $238.2038   $238.20   $238.20   $238.20  
  Purchase #4 $206.78   9.425%   $226.269   $226.27   $226.25   $226.30  
  Purchase #5 $223.65   9.551%   $245.0108   $245.01   $245.00   $245.00  
  Purchase #6 $161.80   3.768%   $167.8966   $167.90   $167.90   $167.90  
  Purchase #7 $117.44   10.230%   $129.4541   $129.45   $129.45   $129.50  
  7 purchase totals = $1,359.44       $1,463.5375   $1,463.53   $1,463.50   $1,463.60