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	$243.27	10.872%	$269.7183	$269.72	$269.70	$269.70
Purchase #2	$75.48	5.514%	$79.642	$79.64	$79.65	$79.60
Purchase #3	$52.46	12.628%	$59.0846	$59.08	$59.10	$59.10
Purchase #4	$243.47	13.144%	$275.4717	$275.47	$275.45	$275.50
Purchase #5	$150.60	9.729%	$165.2519	$165.25	$165.25	$165.30
Purchase #6	$182.37	9.275%	$199.2848	$199.28	$199.30	$199.30
Purchase #7	$107.82	12.273%	$121.0527	$121.05	$121.05	$121.10
7 purchase totals =	$1,055.47		$1,169.5060	$1,169.49	$1,169.50	$1,169.60