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	$205.40	8.297%	$222.442	$222.44	$222.45	$222.40
Purchase #2	$65.64	9.302%	$71.7458	$71.75	$71.75	$71.70
Purchase #3	$46.48	8.595%	$50.475	$50.48	$50.50	$50.50
Purchase #4	$136.52	5.428%	$143.9303	$143.93	$143.95	$143.90
Purchase #5	$59.61	3.681%	$61.8042	$61.80	$61.80	$61.80
Purchase #6	$61.95	6.176%	$65.776	$65.78	$65.80	$65.80
Purchase #7	$173.93	13.819%	$197.9654	$197.97	$197.95	$198.00
7 purchase totals =	$749.53		$814.1387	$814.15	$814.20	$814.10