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	$54.37	6.564%	$57.9388	$57.94	$57.95	$57.90
Purchase #2	$49.25	13.769%	$56.0312	$56.03	$56.05	$56.00
Purchase #3	$9.92	7.628%	$10.6767	$10.68	$10.70	$10.70
Purchase #4	$79.74	5.132%	$83.8323	$83.83	$83.85	$83.80
Purchase #5	$179.73	9.205%	$196.2741	$196.27	$196.25	$196.30
Purchase #6	$123.64	11.316%	$137.6311	$137.63	$137.65	$137.60
Purchase #7	$167.45	10.667%	$185.3119	$185.31	$185.30	$185.30
7 purchase totals =	$664.10		$727.6961	$727.69	$727.75	$727.60