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	$224.73	6.167%	$238.5891	$238.59	$238.60	$238.60
Purchase #2	$150.96	5.747%	$159.6357	$159.64	$159.65	$159.60
Purchase #3	$18.79	3.561%	$19.4591	$19.46	$19.45	$19.50
Purchase #4	$126.85	3.620%	$131.442	$131.44	$131.45	$131.40
Purchase #5	$210.45	5.849%	$222.7592	$222.76	$222.75	$222.80
Purchase #6	$235.32	6.401%	$250.3828	$250.38	$250.40	$250.40
Purchase #7	$236.91	7.653%	$255.0407	$255.04	$255.05	$255.00
7 purchase totals =	$1,204.01		$1,277.3086	$1,277.31	$1,277.35	$1,277.30