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	$166.72	10.192%	$183.7121	$183.71	$183.70	$183.70
Purchase #2	$64.48	4.716%	$67.5209	$67.52	$67.50	$67.50
Purchase #3	$69.60	11.303%	$77.4669	$77.47	$77.45	$77.50
Purchase #4	$71.30	3.150%	$73.546	$73.55	$73.55	$73.50
Purchase #5	$61.44	10.777%	$68.0614	$68.06	$68.05	$68.10
Purchase #6	$71.32	13.317%	$80.8177	$80.82	$80.80	$80.80
Purchase #7	$125.43	3.758%	$130.1437	$130.14	$130.15	$130.10
7 purchase totals =	$630.29		$681.2687	$681.27	$681.20	$681.20