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	$123.31	3.125%	$127.1634	$127.16	$127.15	$127.20
Purchase #2	$161.35	11.572%	$180.0214	$180.02	$180.00	$180.00
Purchase #3	$220.74	11.227%	$245.5225	$245.52	$245.50	$245.50
Purchase #4	$191.43	8.692%	$208.0691	$208.07	$208.05	$208.10
Purchase #5	$39.72	9.315%	$43.4199	$43.42	$43.40	$43.40
Purchase #6	$43.55	3.348%	$45.0081	$45.01	$45.00	$45.00
Purchase #7	$106.27	10.442%	$117.3667	$117.37	$117.35	$117.40
7 purchase totals =	$886.37		$966.5711	$966.57	$966.45	$966.60