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	$236.65	11.172%	$263.0885	$263.09	$263.10	$263.10
Purchase #2	$74.53	13.116%	$84.3054	$84.31	$84.30	$84.30
Purchase #3	$148.82	5.649%	$157.2268	$157.23	$157.25	$157.20
Purchase #4	$165.42	4.304%	$172.5397	$172.54	$172.55	$172.50
Purchase #5	$146.83	6.358%	$156.1655	$156.17	$156.15	$156.20
Purchase #6	$83.40	4.840%	$87.4366	$87.44	$87.45	$87.40
Purchase #7	$78.86	12.208%	$88.4872	$88.49	$88.50	$88.50
7 purchase totals =	$934.51		$1,009.2497	$1,009.27	$1,009.30	$1,009.20