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	$107.26	4.196%	$111.7606	$111.76	$111.75	$111.80
Purchase #2	$89.29	4.679%	$93.4679	$93.47	$93.45	$93.50
Purchase #3	$202.26	8.580%	$219.6139	$219.61	$219.60	$219.60
Purchase #4	$126.62	13.245%	$143.3908	$143.39	$143.40	$143.40
Purchase #5	$206.59	4.668%	$216.2336	$216.23	$216.25	$216.20
Purchase #6	$125.61	8.742%	$136.5908	$136.59	$136.60	$136.60
Purchase #7	$54.42	6.349%	$57.8751	$57.88	$57.90	$57.90
7 purchase totals =	$912.05		$978.9327	$978.93	$978.95	$979.00