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	$199.65	11.745%	$223.0989	$223.10	$223.10	$223.10
Purchase #2	$184.90	13.443%	$209.7561	$209.76	$209.75	$209.80
Purchase #3	$75.29	6.662%	$80.3058	$80.31	$80.30	$80.30
Purchase #4	$107.41	5.734%	$113.5689	$113.57	$113.55	$113.60
Purchase #5	$78.46	10.258%	$86.5084	$86.51	$86.50	$86.50
Purchase #6	$164.84	4.814%	$172.7754	$172.78	$172.80	$172.80
Purchase #7	$105.55	8.451%	$114.47	$114.47	$114.45	$114.50
7 purchase totals =	$916.10		$1,000.4835	$1,000.50	$1,000.45	$1,000.60