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	$155.94	7.685%	$167.924	$167.92	$167.90	$167.90
Purchase #2	$170.38	9.703%	$186.912	$186.91	$186.90	$186.90
Purchase #3	$92.33	10.357%	$101.8926	$101.89	$101.90	$101.90
Purchase #4	$43.78	3.230%	$45.1941	$45.19	$45.20	$45.20
Purchase #5	$249.86	9.299%	$273.0945	$273.09	$273.10	$273.10
Purchase #6	$81.71	11.587%	$91.1777	$91.18	$91.20	$91.20
Purchase #7	$126.81	10.698%	$140.3761	$140.38	$140.40	$140.40
7 purchase totals =	$920.81		$1,006.5710	$1,006.56	$1,006.60	$1,006.60