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	$165.51	6.114%	$175.6293	$175.63	$175.65	$175.60
Purchase #2	$215.92	12.685%	$243.3095	$243.31	$243.30	$243.30
Purchase #3	$144.30	11.243%	$160.5236	$160.52	$160.50	$160.50
Purchase #4	$73.92	6.226%	$78.5223	$78.52	$78.50	$78.50
Purchase #5	$160.75	5.841%	$170.1394	$170.14	$170.15	$170.10
Purchase #6	$239.75	3.686%	$248.5872	$248.59	$248.60	$248.60
Purchase #7	$130.56	5.635%	$137.9171	$137.92	$137.90	$137.90
7 purchase totals =	$1,130.71		$1,214.6284	$1,214.63	$1,214.60	$1,214.50