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	$35.67	5.793%	$37.7364	$37.74	$37.75	$37.70
Purchase #2	$137.25	5.847%	$145.275	$145.28	$145.30	$145.30
Purchase #3	$174.81	9.451%	$191.3313	$191.33	$191.35	$191.30
Purchase #4	$169.40	4.457%	$176.9502	$176.95	$176.95	$177.00
Purchase #5	$36.35	10.157%	$40.0421	$40.04	$40.05	$40.00
Purchase #6	$79.39	11.672%	$88.6564	$88.66	$88.65	$88.70
Purchase #7	$50.31	8.393%	$54.5325	$54.53	$54.55	$54.50
7 purchase totals =	$683.18		$734.5239	$734.53	$734.60	$734.50