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	$195.81	13.780%	$222.7926	$222.79	$222.80	$222.80
Purchase #2	$154.92	6.548%	$165.0642	$165.06	$165.05	$165.10
Purchase #3	$230.48	13.486%	$261.5625	$261.56	$261.55	$261.60
Purchase #4	$192.39	7.214%	$206.269	$206.27	$206.25	$206.30
Purchase #5	$83.85	9.502%	$91.8174	$91.82	$91.80	$91.80
Purchase #6	$245.25	4.696%	$256.7669	$256.77	$256.75	$256.80
Purchase #7	$111.86	11.307%	$124.508	$124.51	$124.50	$124.50
7 purchase totals =	$1,214.56		$1,328.7806	$1,328.78	$1,328.70	$1,328.90