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	$222.55	11.265%	$247.6203	$247.62	$247.60	$247.60
Purchase #2	$49.72	10.172%	$54.7775	$54.78	$54.80	$54.80
Purchase #3	$136.82	6.338%	$145.4917	$145.49	$145.50	$145.50
Purchase #4	$78.90	13.183%	$89.3014	$89.30	$89.30	$89.30
Purchase #5	$216.87	12.531%	$244.046	$244.05	$244.05	$244.00
Purchase #6	$60.37	11.364%	$67.2304	$67.23	$67.25	$67.20
Purchase #7	$175.64	10.166%	$193.4956	$193.50	$193.50	$193.50
7 purchase totals =	$940.87		$1,041.9629	$1,041.97	$1,042.00	$1,041.90