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	$96.95	3.302%	$100.1513	$100.15	$100.15	$100.20
Purchase #2	$171.38	9.700%	$188.0039	$188.00	$188.00	$188.00
Purchase #3	$185.27	3.326%	$191.4321	$191.43	$191.45	$191.40
Purchase #4	$124.40	4.168%	$129.585	$129.59	$129.60	$129.60
Purchase #5	$231.33	10.550%	$255.7353	$255.74	$255.75	$255.70
Purchase #6	$17.78	7.109%	$19.044	$19.04	$19.05	$19.00
Purchase #7	$127.71	4.647%	$133.6447	$133.64	$133.65	$133.60
7 purchase totals =	$954.82		$1,017.5963	$1,017.59	$1,017.65	$1,017.50