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	$208.87	12.490%	$234.9579	$234.96	$234.95	$235.00
Purchase #2	$138.66	10.809%	$153.6478	$153.65	$153.65	$153.60
Purchase #3	$205.52	11.600%	$229.3603	$229.36	$229.35	$229.40
Purchase #4	$212.98	13.718%	$242.1966	$242.20	$242.20	$242.20
Purchase #5	$47.57	6.105%	$50.4741	$50.47	$50.45	$50.50
Purchase #6	$176.73	5.187%	$185.897	$185.90	$185.90	$185.90
Purchase #7	$50.52	9.543%	$55.3411	$55.34	$55.35	$55.30
7 purchase totals =	$1,040.85		$1,151.8748	$1,151.88	$1,151.85	$1,151.90