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 $65.68   11.212%   $73.044   $73.04   $73.05   $73.00  
  Purchase #2 $213.64   5.297%   $224.9565   $224.96   $224.95   $225.00  
  Purchase #3 $149.53   9.109%   $163.1507   $163.15   $163.15   $163.20  
  Purchase #4 $101.29   8.599%   $109.9999   $110.00   $110.00   $110.00  
  Purchase #5 $206.53   11.457%   $230.1921   $230.19   $230.20   $230.20  
  Purchase #6 $137.90   4.397%   $143.9635   $143.96   $143.95   $144.00  
  Purchase #7 $159.74   3.856%   $165.8996   $165.90   $165.90   $165.90  
  7 purchase totals = $1,034.31       $1,111.2063   $1,111.20   $1,111.20   $1,111.30