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	$200.93	9.869%	$220.7598	$220.76	$220.75	$220.80
Purchase #2	$79.38	12.271%	$89.1207	$89.12	$89.10	$89.10
Purchase #3	$109.89	4.509%	$114.8449	$114.84	$114.85	$114.80
Purchase #4	$181.38	8.273%	$196.3856	$196.39	$196.40	$196.40
Purchase #5	$49.81	7.178%	$53.3854	$53.39	$53.40	$53.40
Purchase #6	$158.54	7.656%	$170.6778	$170.68	$170.70	$170.70
Purchase #7	$84.67	12.810%	$95.5162	$95.52	$95.50	$95.50
7 purchase totals =	$864.60		$940.6904	$940.70	$940.70	$940.70