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 $182.82   13.760%   $207.976   $207.98   $208.00   $208.00  
  Purchase #2 $6.77   8.408%   $7.3392   $7.34   $7.35   $7.30  
  Purchase #3 $158.26   4.687%   $165.6776   $165.68   $165.70   $165.70  
  Purchase #4 $203.85   3.466%   $210.9154   $210.92   $210.90   $210.90  
  Purchase #5 $246.83   6.515%   $262.911   $262.91   $262.90   $262.90  
  Purchase #6 $194.96   9.508%   $213.4968   $213.50   $213.50   $213.50  
  Purchase #7 $43.41   4.839%   $45.5106   $45.51   $45.50   $45.50  
  7 purchase totals = $1,036.90       $1,113.8266   $1,113.84   $1,113.85   $1,113.80