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	$41.76	12.205%	$46.8568	$46.86	$46.85	$46.90
Purchase #2	$62.66	4.601%	$65.543	$65.54	$65.55	$65.50
Purchase #3	$197.99	10.666%	$219.1076	$219.11	$219.10	$219.10
Purchase #4	$167.89	13.329%	$190.2681	$190.27	$190.25	$190.30
Purchase #5	$19.68	4.153%	$20.4973	$20.50	$20.50	$20.50
Purchase #6	$122.52	7.116%	$131.2385	$131.24	$131.25	$131.20
Purchase #7	$57.72	8.337%	$62.5321	$62.53	$62.55	$62.50
7 purchase totals =	$670.22		$736.0434	$736.05	$736.05	$736.00