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	$158.98	5.133%	$167.1404	$167.14	$167.15	$167.10
Purchase #2	$38.48	13.122%	$43.5293	$43.53	$43.55	$43.50
Purchase #3	$33.45	5.390%	$35.253	$35.25	$35.25	$35.30
Purchase #4	$247.50	6.444%	$263.4489	$263.45	$263.45	$263.40
Purchase #5	$31.29	6.725%	$33.3943	$33.39	$33.40	$33.40
Purchase #6	$75.51	8.114%	$81.6369	$81.64	$81.65	$81.60
Purchase #7	$141.31	10.150%	$155.653	$155.65	$155.65	$155.70
7 purchase totals =	$726.52		$780.0558	$780.05	$780.10	$780.00