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	$71.25	3.365%	$73.6476	$73.65	$73.65	$73.60
Purchase #2	$60.58	11.237%	$67.3874	$67.39	$67.40	$67.40
Purchase #3	$233.37	4.196%	$243.1622	$243.16	$243.15	$243.20
Purchase #4	$52.68	12.840%	$59.4441	$59.44	$59.45	$59.40
Purchase #5	$62.72	8.242%	$67.8894	$67.89	$67.90	$67.90
Purchase #6	$227.31	5.849%	$240.6054	$240.61	$240.60	$240.60
Purchase #7	$171.61	9.773%	$188.3814	$188.38	$188.40	$188.40
7 purchase totals =	$879.52		$940.5175	$940.52	$940.55	$940.50