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	$41.31	6.665%	$44.0633	$44.06	$44.05	$44.10
Purchase #2	$152.53	8.145%	$164.9536	$164.95	$164.95	$165.00
Purchase #3	$104.77	9.668%	$114.8992	$114.90	$114.90	$114.90
Purchase #4	$11.57	6.453%	$12.3166	$12.32	$12.30	$12.30
Purchase #5	$89.52	12.131%	$100.3797	$100.38	$100.40	$100.40
Purchase #6	$100.56	11.773%	$112.3989	$112.40	$112.40	$112.40
Purchase #7	$219.72	7.178%	$235.4915	$235.49	$235.50	$235.50
7 purchase totals =	$719.98		$784.5028	$784.50	$784.50	$784.60