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	$167.66	10.431%	$185.1486	$185.15	$185.15	$185.10
Purchase #2	$100.56	5.276%	$105.8655	$105.87	$105.85	$105.90
Purchase #3	$173.64	10.107%	$191.1898	$191.19	$191.20	$191.20
Purchase #4	$136.44	3.404%	$141.0844	$141.08	$141.10	$141.10
Purchase #5	$158.30	4.779%	$165.8652	$165.87	$165.85	$165.90
Purchase #6	$50.89	4.305%	$53.0808	$53.08	$53.10	$53.10
Purchase #7	$183.68	11.248%	$204.3403	$204.34	$204.35	$204.30
7 purchase totals =	$971.17		$1,046.5746	$1,046.58	$1,046.60	$1,046.60