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	$133.37	10.629%	$147.5459	$147.55	$147.55	$147.50
Purchase #2	$14.74	5.677%	$15.5768	$15.58	$15.60	$15.60
Purchase #3	$126.78	11.339%	$141.1556	$141.16	$141.15	$141.20
Purchase #4	$148.75	6.782%	$158.8382	$158.84	$158.85	$158.80
Purchase #5	$93.73	5.812%	$99.1776	$99.18	$99.20	$99.20
Purchase #6	$228.72	5.709%	$241.7776	$241.78	$241.80	$241.80
Purchase #7	$189.78	7.180%	$203.4062	$203.41	$203.40	$203.40
7 purchase totals =	$935.87		$1,007.4779	$1,007.50	$1,007.55	$1,007.50