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 $65.93   11.483%   $73.5007   $73.50   $73.50   $73.50  
  Purchase #2 $41.33   5.360%   $43.5453   $43.55   $43.55   $43.50  
  Purchase #3 $30.85   9.490%   $33.7777   $33.78   $33.80   $33.80  
  Purchase #4 $157.61   6.134%   $167.2778   $167.28   $167.30   $167.30  
  Purchase #5 $179.34   9.565%   $196.4939   $196.49   $196.50   $196.50  
  Purchase #6 $21.65   7.836%   $23.3465   $23.35   $23.35   $23.30  
  Purchase #7 $180.55   7.554%   $194.1887   $194.19   $194.20   $194.20  
  7 purchase totals = $677.26       $732.1306   $732.14   $732.20   $732.10