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	$152.79	11.563%	$170.4571	$170.46	$170.45	$170.50
Purchase #2	$165.42	13.406%	$187.5962	$187.60	$187.60	$187.60
Purchase #3	$197.36	4.128%	$205.507	$205.51	$205.50	$205.50
Purchase #4	$184.87	6.429%	$196.7553	$196.76	$196.75	$196.80
Purchase #5	$222.41	13.504%	$252.4442	$252.44	$252.45	$252.40
Purchase #6	$234.36	6.267%	$249.0473	$249.05	$249.05	$249.00
Purchase #7	$160.45	4.790%	$168.1356	$168.14	$168.15	$168.10
7 purchase totals =	$1,317.66		$1,429.9427	$1,429.96	$1,429.95	$1,429.90