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	$184.55	3.250%	$190.5479	$190.55	$190.55	$190.50
Purchase #2	$50.65	7.821%	$54.6113	$54.61	$54.60	$54.60
Purchase #3	$11.44	9.224%	$12.4952	$12.50	$12.50	$12.50
Purchase #4	$25.25	4.163%	$26.3012	$26.30	$26.30	$26.30
Purchase #5	$78.58	9.308%	$85.8942	$85.89	$85.90	$85.90
Purchase #6	$172.50	13.414%	$195.6392	$195.64	$195.65	$195.60
Purchase #7	$248.79	9.341%	$272.0295	$272.03	$272.05	$272.00
7 purchase totals =	$771.76		$837.5185	$837.52	$837.55	$837.40