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	$114.45	11.463%	$127.5694	$127.57	$127.55	$127.60
Purchase #2	$246.42	5.262%	$259.3866	$259.39	$259.40	$259.40
Purchase #3	$160.65	5.705%	$169.8151	$169.82	$169.80	$169.80
Purchase #4	$90.58	5.679%	$95.724	$95.72	$95.70	$95.70
Purchase #5	$166.72	9.115%	$181.9165	$181.92	$181.90	$181.90
Purchase #6	$110.38	11.485%	$123.0571	$123.06	$123.05	$123.10
Purchase #7	$15.70	3.847%	$16.304	$16.30	$16.30	$16.30
7 purchase totals =	$904.90		$973.7727	$973.78	$973.70	$973.80