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	$211.28	8.653%	$229.5621	$229.56	$229.55	$229.60
Purchase #2	$192.25	5.387%	$202.6065	$202.61	$202.60	$202.60
Purchase #3	$184.48	11.399%	$205.5089	$205.51	$205.50	$205.50
Purchase #4	$90.91	11.378%	$101.2537	$101.25	$101.25	$101.30
Purchase #5	$36.71	4.622%	$38.4067	$38.41	$38.40	$38.40
Purchase #6	$170.50	11.719%	$190.4809	$190.48	$190.50	$190.50
Purchase #7	$42.46	13.363%	$48.1339	$48.13	$48.15	$48.10
7 purchase totals =	$928.59		$1,015.9527	$1,015.95	$1,015.95	$1,016.00