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	$28.84	6.201%	$30.6284	$30.63	$30.65	$30.60
Purchase #2	$95.61	4.829%	$100.227	$100.23	$100.25	$100.20
Purchase #3	$102.51	8.337%	$111.0563	$111.06	$111.05	$111.10
Purchase #4	$95.31	5.690%	$100.7331	$100.73	$100.75	$100.70
Purchase #5	$167.44	8.361%	$181.4397	$181.44	$181.45	$181.40
Purchase #6	$224.62	9.102%	$245.0649	$245.06	$245.05	$245.10
Purchase #7	$244.39	3.435%	$252.7848	$252.78	$252.80	$252.80
7 purchase totals =	$958.72		$1,021.9342	$1,021.93	$1,022.00	$1,021.90