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	$233.30	3.243%	$240.8659	$240.87	$240.85	$240.90
Purchase #2	$40.54	4.220%	$42.2508	$42.25	$42.25	$42.30
Purchase #3	$166.84	3.628%	$172.893	$172.89	$172.90	$172.90
Purchase #4	$35.75	3.202%	$36.8947	$36.89	$36.90	$36.90
Purchase #5	$248.28	9.589%	$272.0876	$272.09	$272.10	$272.10
Purchase #6	$214.47	8.140%	$231.9279	$231.93	$231.95	$231.90
Purchase #7	$33.56	8.188%	$36.3079	$36.31	$36.30	$36.30
7 purchase totals =	$972.74		$1,033.2278	$1,033.23	$1,033.25	$1,033.30