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	$32.98	4.871%	$34.5865	$34.59	$34.60	$34.60
Purchase #2	$105.39	8.675%	$114.5326	$114.53	$114.55	$114.50
Purchase #3	$145.91	3.682%	$151.2824	$151.28	$151.30	$151.30
Purchase #4	$16.26	12.670%	$18.3201	$18.32	$18.30	$18.30
Purchase #5	$243.54	10.651%	$269.4794	$269.48	$269.50	$269.50
Purchase #6	$49.52	6.416%	$52.6972	$52.70	$52.70	$52.70
Purchase #7	$31.57	12.451%	$35.5008	$35.50	$35.50	$35.50
7 purchase totals =	$625.17		$676.3990	$676.40	$676.45	$676.40