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	$157.63	10.290%	$173.8501	$173.85	$173.85	$173.90
Purchase #2	$133.38	3.788%	$138.4324	$138.43	$138.45	$138.40
Purchase #3	$151.27	11.636%	$168.8718	$168.87	$168.85	$168.90
Purchase #4	$50.28	6.874%	$53.7362	$53.74	$53.75	$53.70
Purchase #5	$247.70	3.537%	$256.4611	$256.46	$256.45	$256.50
Purchase #6	$151.49	5.371%	$159.6265	$159.63	$159.65	$159.60
Purchase #7	$166.95	5.110%	$175.4811	$175.48	$175.50	$175.50
7 purchase totals =	$1,058.70		$1,126.4592	$1,126.46	$1,126.50	$1,126.50