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	$208.96	9.667%	$229.1602	$229.16	$229.15	$229.20
Purchase #2	$27.61	13.468%	$31.3285	$31.33	$31.35	$31.30
Purchase #3	$66.65	12.212%	$74.7893	$74.79	$74.80	$74.80
Purchase #4	$223.66	3.472%	$231.4255	$231.43	$231.45	$231.40
Purchase #5	$212.43	11.231%	$236.288	$236.29	$236.30	$236.30
Purchase #6	$200.33	6.708%	$213.7681	$213.77	$213.75	$213.80
Purchase #7	$74.88	10.606%	$82.8218	$82.82	$82.80	$82.80
7 purchase totals =	$1,014.52		$1,099.5814	$1,099.59	$1,099.60	$1,099.60