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	$199.90	4.782%	$209.4592	$209.46	$209.45	$209.50
Purchase #2	$129.53	13.243%	$146.6837	$146.68	$146.70	$146.70
Purchase #3	$64.33	11.272%	$71.5813	$71.58	$71.60	$71.60
Purchase #4	$76.54	10.407%	$84.5055	$84.51	$84.50	$84.50
Purchase #5	$57.55	6.667%	$61.3869	$61.39	$61.40	$61.40
Purchase #6	$239.40	8.697%	$260.2206	$260.22	$260.20	$260.20
Purchase #7	$167.52	11.376%	$186.5771	$186.58	$186.60	$186.60
7 purchase totals =	$934.77		$1,020.4143	$1,020.42	$1,020.45	$1,020.50