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	$85.73	3.424%	$88.6654	$88.67	$88.65	$88.70
Purchase #2	$75.45	4.381%	$78.7555	$78.76	$78.75	$78.80
Purchase #3	$148.85	4.540%	$155.6078	$155.61	$155.60	$155.60
Purchase #4	$158.29	6.166%	$168.0502	$168.05	$168.05	$168.10
Purchase #5	$96.80	11.194%	$107.6358	$107.64	$107.65	$107.60
Purchase #6	$226.95	5.114%	$238.5562	$238.56	$238.55	$238.60
Purchase #7	$138.63	5.354%	$146.0523	$146.05	$146.05	$146.10
7 purchase totals =	$930.70		$983.3232	$983.34	$983.30	$983.50