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	$236.82	8.225%	$256.2984	$256.30	$256.30	$256.30
Purchase #2	$213.54	6.495%	$227.4094	$227.41	$227.40	$227.40
Purchase #3	$67.79	8.574%	$73.6023	$73.60	$73.60	$73.60
Purchase #4	$246.64	5.374%	$259.8944	$259.89	$259.90	$259.90
Purchase #5	$59.91	3.407%	$61.9511	$61.95	$61.95	$62.00
Purchase #6	$103.51	10.806%	$114.6953	$114.70	$114.70	$114.70
Purchase #7	$144.61	10.313%	$159.5236	$159.52	$159.50	$159.50
7 purchase totals =	$1,072.82		$1,153.3745	$1,153.37	$1,153.35	$1,153.40