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	$168.99	7.198%	$181.1539	$181.15	$181.15	$181.20
Purchase #2	$19.39	5.244%	$20.4068	$20.41	$20.40	$20.40
Purchase #3	$141.49	12.843%	$159.6616	$159.66	$159.65	$159.70
Purchase #4	$89.55	10.446%	$98.9044	$98.90	$98.90	$98.90
Purchase #5	$57.85	4.617%	$60.5209	$60.52	$60.50	$60.50
Purchase #6	$172.75	7.478%	$185.6682	$185.67	$185.65	$185.70
Purchase #7	$27.85	6.104%	$29.55	$29.55	$29.55	$29.60
7 purchase totals =	$677.87		$735.8658	$735.86	$735.80	$736.00