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	$136.65	6.540%	$145.5869	$145.59	$145.60	$145.60
Purchase #2	$222.34	11.159%	$247.1509	$247.15	$247.15	$247.20
Purchase #3	$195.62	10.546%	$216.2501	$216.25	$216.25	$216.30
Purchase #4	$12.83	5.838%	$13.579	$13.58	$13.60	$13.60
Purchase #5	$72.34	3.869%	$75.1388	$75.14	$75.15	$75.10
Purchase #6	$220.85	7.390%	$237.1708	$237.17	$237.15	$237.20
Purchase #7	$123.63	6.344%	$131.4731	$131.47	$131.45	$131.50
7 purchase totals =	$984.26		$1,066.3496	$1,066.35	$1,066.35	$1,066.50