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	$56.54	4.670%	$59.1804	$59.18	$59.20	$59.20
Purchase #2	$213.59	5.150%	$224.5899	$224.59	$224.60	$224.60
Purchase #3	$45.38	4.870%	$47.59	$47.59	$47.60	$47.60
Purchase #4	$74.75	7.231%	$80.1552	$80.16	$80.15	$80.20
Purchase #5	$137.43	6.682%	$146.6131	$146.61	$146.60	$146.60
Purchase #6	$244.48	3.105%	$252.0711	$252.07	$252.05	$252.10
Purchase #7	$172.44	8.553%	$187.1888	$187.19	$187.20	$187.20
7 purchase totals =	$944.61		$997.3885	$997.39	$997.40	$997.50