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	$223.89	10.607%	$247.638	$247.64	$247.65	$247.60
Purchase #2	$17.30	4.411%	$18.0631	$18.06	$18.05	$18.10
Purchase #3	$152.84	8.346%	$165.596	$165.60	$165.60	$165.60
Purchase #4	$223.82	10.400%	$247.0973	$247.10	$247.10	$247.10
Purchase #5	$204.49	11.211%	$227.4154	$227.42	$227.40	$227.40
Purchase #6	$105.85	3.544%	$109.6013	$109.60	$109.60	$109.60
Purchase #7	$64.79	3.432%	$67.0136	$67.01	$67.00	$67.00
7 purchase totals =	$992.98		$1,082.4247	$1,082.43	$1,082.40	$1,082.40