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	$111.41	13.573%	$126.5317	$126.53	$126.55	$126.50
Purchase #2	$35.37	6.251%	$37.581	$37.58	$37.60	$37.60
Purchase #3	$148.91	5.106%	$156.5133	$156.51	$156.50	$156.50
Purchase #4	$73.93	11.471%	$82.4105	$82.41	$82.40	$82.40
Purchase #5	$239.26	12.425%	$268.9881	$268.99	$269.00	$269.00
Purchase #6	$250.58	9.692%	$274.8662	$274.87	$274.85	$274.90
Purchase #7	$97.31	10.553%	$107.5791	$107.58	$107.60	$107.60
7 purchase totals =	$956.77		$1,054.4699	$1,054.47	$1,054.50	$1,054.50