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	$92.45	11.791%	$103.3508	$103.35	$103.35	$103.40
Purchase #2	$151.38	5.405%	$159.5621	$159.56	$159.55	$159.60
Purchase #3	$48.91	12.755%	$55.1485	$55.15	$55.15	$55.10
Purchase #4	$171.81	13.791%	$195.5043	$195.50	$195.50	$195.50
Purchase #5	$192.93	6.378%	$205.2351	$205.24	$205.25	$205.20
Purchase #6	$114.83	13.598%	$130.4446	$130.44	$130.45	$130.40
Purchase #7	$49.50	9.742%	$54.3223	$54.32	$54.30	$54.30
7 purchase totals =	$821.81		$903.5677	$903.56	$903.55	$903.50