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	$50.30	6.654%	$53.647	$53.65	$53.65	$53.60
Purchase #2	$139.36	3.280%	$143.931	$143.93	$143.95	$143.90
Purchase #3	$119.34	6.853%	$127.5184	$127.52	$127.50	$127.50
Purchase #4	$193.58	7.843%	$208.7625	$208.76	$208.75	$208.80
Purchase #5	$233.83	12.242%	$262.4555	$262.46	$262.45	$262.50
Purchase #6	$145.57	9.479%	$159.3686	$159.37	$159.35	$159.40
Purchase #7	$240.37	4.488%	$251.1578	$251.16	$251.15	$251.20
7 purchase totals =	$1,122.35		$1,206.8408	$1,206.85	$1,206.80	$1,206.90