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	$176.62	11.762%	$197.394	$197.39	$197.40	$197.40
Purchase #2	$151.60	5.476%	$159.9016	$159.90	$159.90	$159.90
Purchase #3	$239.42	4.196%	$249.4661	$249.47	$249.45	$249.50
Purchase #4	$58.56	13.824%	$66.6553	$66.66	$66.65	$66.70
Purchase #5	$167.29	12.265%	$187.8081	$187.81	$187.80	$187.80
Purchase #6	$220.75	13.388%	$250.304	$250.30	$250.30	$250.30
Purchase #7	$142.96	10.435%	$157.8779	$157.88	$157.90	$157.90
7 purchase totals =	$1,157.20		$1,269.4070	$1,269.41	$1,269.40	$1,269.50