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	$32.29	12.845%	$36.4377	$36.44	$36.45	$36.40
Purchase #2	$128.72	12.291%	$144.541	$144.54	$144.55	$144.50
Purchase #3	$85.49	4.825%	$89.6149	$89.61	$89.60	$89.60
Purchase #4	$208.95	11.860%	$233.7315	$233.73	$233.75	$233.70
Purchase #5	$236.42	4.227%	$246.4135	$246.41	$246.40	$246.40
Purchase #6	$204.48	10.481%	$225.9115	$225.91	$225.90	$225.90
Purchase #7	$133.66	13.202%	$151.3058	$151.31	$151.30	$151.30
7 purchase totals =	$1,030.01		$1,127.9559	$1,127.95	$1,127.95	$1,127.80