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	$216.25	6.314%	$229.904	$229.90	$229.90	$229.90
Purchase #2	$167.90	4.663%	$175.7292	$175.73	$175.75	$175.70
Purchase #3	$176.54	8.855%	$192.1726	$192.17	$192.15	$192.20
Purchase #4	$142.25	4.271%	$148.3255	$148.33	$148.35	$148.30
Purchase #5	$81.58	13.478%	$92.5754	$92.58	$92.60	$92.60
Purchase #6	$110.71	3.262%	$114.3214	$114.32	$114.30	$114.30
Purchase #7	$42.89	13.801%	$48.8092	$48.81	$48.80	$48.80
7 purchase totals =	$938.12		$1,001.8373	$1,001.84	$1,001.85	$1,001.80