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	$139.61	8.463%	$151.4252	$151.43	$151.45	$151.40
Purchase #2	$75.89	10.849%	$84.1233	$84.12	$84.10	$84.10
Purchase #3	$85.73	10.544%	$94.7694	$94.77	$94.75	$94.80
Purchase #4	$100.58	10.539%	$111.1801	$111.18	$111.20	$111.20
Purchase #5	$84.92	13.764%	$96.6084	$96.61	$96.60	$96.60
Purchase #6	$58.32	5.563%	$61.5643	$61.56	$61.55	$61.60
Purchase #7	$110.69	5.634%	$116.9263	$116.93	$116.95	$116.90
7 purchase totals =	$655.74		$716.5970	$716.60	$716.60	$716.60