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	$215.51	10.588%	$238.3282	$238.33	$238.35	$238.30
Purchase #2	$203.69	11.145%	$226.3913	$226.39	$226.40	$226.40
Purchase #3	$230.56	6.554%	$245.6709	$245.67	$245.65	$245.70
Purchase #4	$33.76	5.698%	$35.6836	$35.68	$35.70	$35.70
Purchase #5	$243.52	5.143%	$256.0442	$256.04	$256.05	$256.00
Purchase #6	$66.89	4.829%	$70.1201	$70.12	$70.10	$70.10
Purchase #7	$35.80	3.789%	$37.1565	$37.16	$37.15	$37.20
7 purchase totals =	$1,029.73		$1,109.3948	$1,109.39	$1,109.40	$1,109.40