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	$14.44	5.410%	$15.2212	$15.22	$15.20	$15.20
Purchase #2	$233.58	12.712%	$263.2727	$263.27	$263.25	$263.30
Purchase #3	$238.72	11.148%	$265.3325	$265.33	$265.35	$265.30
Purchase #4	$78.39	6.562%	$83.534	$83.53	$83.55	$83.50
Purchase #5	$230.51	12.431%	$259.1647	$259.16	$259.15	$259.20
Purchase #6	$175.77	8.591%	$190.8704	$190.87	$190.85	$190.90
Purchase #7	$18.95	4.715%	$19.8435	$19.84	$19.85	$19.80
7 purchase totals =	$990.36		$1,097.2390	$1,097.22	$1,097.20	$1,097.20