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	$106.54	5.408%	$112.3017	$112.30	$112.30	$112.30
Purchase #2	$17.89	10.488%	$19.7663	$19.77	$19.75	$19.80
Purchase #3	$171.94	10.501%	$189.9954	$190.00	$190.00	$190.00
Purchase #4	$198.43	12.245%	$222.7278	$222.73	$222.75	$222.70
Purchase #5	$73.43	5.594%	$77.5377	$77.54	$77.55	$77.50
Purchase #6	$131.33	11.194%	$146.0311	$146.03	$146.05	$146.00
Purchase #7	$165.82	9.251%	$181.16	$181.16	$181.15	$181.20
7 purchase totals =	$865.38		$949.5200	$949.53	$949.55	$949.50