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	$9.69	12.518%	$10.903	$10.90	$10.90	$10.90
Purchase #2	$43.25	10.214%	$47.6676	$47.67	$47.65	$47.70
Purchase #3	$149.72	10.689%	$165.7236	$165.72	$165.70	$165.70
Purchase #4	$148.69	6.301%	$158.059	$158.06	$158.05	$158.10
Purchase #5	$46.81	7.603%	$50.369	$50.37	$50.35	$50.40
Purchase #6	$85.61	11.404%	$95.373	$95.37	$95.35	$95.40
Purchase #7	$59.27	8.500%	$64.308	$64.31	$64.30	$64.30
7 purchase totals =	$543.04		$592.4032	$592.40	$592.30	$592.50