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	$114.75	13.403%	$130.1299	$130.13	$130.15	$130.10
Purchase #2	$40.49	11.211%	$45.0293	$45.03	$45.05	$45.00
Purchase #3	$99.59	11.597%	$111.1395	$111.14	$111.15	$111.10
Purchase #4	$73.68	9.756%	$80.8682	$80.87	$80.85	$80.90
Purchase #5	$163.65	9.561%	$179.2966	$179.30	$179.30	$179.30
Purchase #6	$105.51	9.752%	$115.7993	$115.80	$115.80	$115.80
Purchase #7	$238.86	10.262%	$263.3718	$263.37	$263.35	$263.40
7 purchase totals =	$836.53		$925.6346	$925.64	$925.65	$925.60