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	$135.96	11.430%	$151.5002	$151.50	$151.50	$151.50
Purchase #2	$177.32	6.274%	$188.4451	$188.45	$188.45	$188.40
Purchase #3	$169.78	12.816%	$191.539	$191.54	$191.55	$191.50
Purchase #4	$239.52	3.334%	$247.5056	$247.51	$247.50	$247.50
Purchase #5	$17.50	10.786%	$19.3876	$19.39	$19.40	$19.40
Purchase #6	$153.66	12.433%	$172.7645	$172.76	$172.75	$172.80
Purchase #7	$58.54	10.153%	$64.4836	$64.48	$64.50	$64.50
7 purchase totals =	$952.28		$1,035.6256	$1,035.63	$1,035.65	$1,035.60