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	$139.33	3.788%	$144.6078	$144.61	$144.60	$144.60
Purchase #2	$149.53	5.698%	$158.0502	$158.05	$158.05	$158.10
Purchase #3	$110.40	5.556%	$116.5338	$116.53	$116.55	$116.50
Purchase #4	$30.92	6.635%	$32.9715	$32.97	$32.95	$33.00
Purchase #5	$12.80	4.243%	$13.3431	$13.34	$13.35	$13.30
Purchase #6	$95.53	13.146%	$108.0884	$108.09	$108.10	$108.10
Purchase #7	$58.32	5.765%	$61.6821	$61.68	$61.70	$61.70
7 purchase totals =	$596.83		$635.2769	$635.27	$635.30	$635.30