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	$113.69	12.356%	$127.7375	$127.74	$127.75	$127.70
Purchase #2	$50.50	4.509%	$52.777	$52.78	$52.80	$52.80
Purchase #3	$155.29	10.449%	$171.5163	$171.52	$171.50	$171.50
Purchase #4	$24.80	10.806%	$27.4799	$27.48	$27.50	$27.50
Purchase #5	$10.75	8.469%	$11.6604	$11.66	$11.65	$11.70
Purchase #6	$135.86	12.138%	$152.3507	$152.35	$152.35	$152.40
Purchase #7	$79.42	4.275%	$82.8152	$82.82	$82.80	$82.80
7 purchase totals =	$570.31		$626.3370	$626.35	$626.35	$626.40