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	$185.97	5.581%	$196.349	$196.35	$196.35	$196.30
Purchase #2	$45.97	5.858%	$48.6629	$48.66	$48.65	$48.70
Purchase #3	$185.55	10.251%	$204.5707	$204.57	$204.55	$204.60
Purchase #4	$13.31	4.156%	$13.8632	$13.86	$13.85	$13.90
Purchase #5	$13.29	8.586%	$14.4311	$14.43	$14.45	$14.40
Purchase #6	$88.76	11.841%	$99.2701	$99.27	$99.25	$99.30
Purchase #7	$248.75	9.235%	$271.7221	$271.72	$271.70	$271.70
7 purchase totals =	$781.60		$848.8691	$848.86	$848.80	$848.90