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	$146.29	8.860%	$159.2513	$159.25	$159.25	$159.30
Purchase #2	$90.73	9.719%	$99.548	$99.55	$99.55	$99.50
Purchase #3	$186.83	11.260%	$207.8671	$207.87	$207.85	$207.90
Purchase #4	$173.82	7.198%	$186.3316	$186.33	$186.35	$186.30
Purchase #5	$125.97	12.664%	$141.9228	$141.92	$141.90	$141.90
Purchase #6	$101.96	3.742%	$105.7753	$105.78	$105.80	$105.80
Purchase #7	$83.47	3.762%	$86.6101	$86.61	$86.60	$86.60
7 purchase totals =	$909.07		$987.3062	$987.31	$987.30	$987.30