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	$63.63	13.668%	$72.3269	$72.33	$72.35	$72.30
Purchase #2	$50.46	3.452%	$52.2019	$52.20	$52.20	$52.20
Purchase #3	$47.85	4.323%	$49.9186	$49.92	$49.90	$49.90
Purchase #4	$163.39	13.445%	$185.3578	$185.36	$185.35	$185.40
Purchase #5	$164.51	5.263%	$173.1682	$173.17	$173.15	$173.20
Purchase #6	$46.72	13.691%	$53.1164	$53.12	$53.10	$53.10
Purchase #7	$144.48	10.678%	$159.9076	$159.91	$159.90	$159.90
7 purchase totals =	$681.04		$745.9974	$746.01	$745.95	$746.00