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	$55.61	4.245%	$57.9706	$57.97	$57.95	$58.00
Purchase #2	$240.56	13.186%	$272.2802	$272.28	$272.30	$272.30
Purchase #3	$53.66	7.335%	$57.596	$57.60	$57.60	$57.60
Purchase #4	$231.60	5.401%	$244.1087	$244.11	$244.10	$244.10
Purchase #5	$38.94	5.182%	$40.9579	$40.96	$40.95	$41.00
Purchase #6	$176.60	11.293%	$196.5434	$196.54	$196.55	$196.50
Purchase #7	$113.83	9.505%	$124.6495	$124.65	$124.65	$124.60
7 purchase totals =	$910.80		$994.1063	$994.11	$994.10	$994.10