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	$35.37	5.648%	$37.3677	$37.37	$37.35	$37.40
Purchase #2	$108.39	13.514%	$123.0378	$123.04	$123.05	$123.00
Purchase #3	$241.85	3.653%	$250.6848	$250.68	$250.70	$250.70
Purchase #4	$20.60	8.353%	$22.3207	$22.32	$22.30	$22.30
Purchase #5	$74.94	6.626%	$79.9055	$79.91	$79.90	$79.90
Purchase #6	$168.97	12.334%	$189.8108	$189.81	$189.80	$189.80
Purchase #7	$49.63	11.683%	$55.4283	$55.43	$55.45	$55.40
7 purchase totals =	$699.75		$758.5556	$758.56	$758.55	$758.50