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	$27.41	6.272%	$29.1292	$29.13	$29.15	$29.10
Purchase #2	$238.72	8.452%	$258.8966	$258.90	$258.90	$258.90
Purchase #3	$9.65	4.747%	$10.1081	$10.11	$10.10	$10.10
Purchase #4	$225.66	12.588%	$254.0661	$254.07	$254.05	$254.10
Purchase #5	$53.78	10.848%	$59.6141	$59.61	$59.60	$59.60
Purchase #6	$156.91	3.602%	$162.5619	$162.56	$162.55	$162.60
Purchase #7	$216.94	7.202%	$232.564	$232.56	$232.55	$232.60
7 purchase totals =	$929.07		$1,006.9400	$1,006.94	$1,006.90	$1,007.00