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	$124.46	7.126%	$133.329	$133.33	$133.35	$133.30
Purchase #2	$183.61	4.779%	$192.3847	$192.38	$192.40	$192.40
Purchase #3	$230.26	6.252%	$244.6559	$244.66	$244.65	$244.70
Purchase #4	$37.52	13.379%	$42.5398	$42.54	$42.55	$42.50
Purchase #5	$230.81	7.389%	$247.8646	$247.86	$247.85	$247.90
Purchase #6	$86.80	3.704%	$90.0151	$90.02	$90.00	$90.00
Purchase #7	$153.71	9.865%	$168.8735	$168.87	$168.85	$168.90
7 purchase totals =	$1,047.17		$1,119.6626	$1,119.66	$1,119.65	$1,119.70