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	$32.85	3.497%	$33.9988	$34.00	$34.00	$34.00
Purchase #2	$95.28	12.699%	$107.3796	$107.38	$107.40	$107.40
Purchase #3	$158.39	6.392%	$168.5143	$168.51	$168.50	$168.50
Purchase #4	$91.60	4.373%	$95.6057	$95.61	$95.60	$95.60
Purchase #5	$45.27	10.709%	$50.118	$50.12	$50.10	$50.10
Purchase #6	$14.33	6.725%	$15.2937	$15.29	$15.30	$15.30
Purchase #7	$112.84	5.199%	$118.7066	$118.71	$118.70	$118.70
7 purchase totals =	$550.56		$589.6167	$589.62	$589.60	$589.60