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	$109.91	3.381%	$113.6261	$113.63	$113.65	$113.60
Purchase #2	$103.50	4.390%	$108.0437	$108.04	$108.05	$108.00
Purchase #3	$224.89	5.114%	$236.3909	$236.39	$236.40	$236.40
Purchase #4	$241.93	5.173%	$254.445	$254.45	$254.45	$254.40
Purchase #5	$188.77	4.198%	$196.6946	$196.69	$196.70	$196.70
Purchase #6	$85.75	6.652%	$91.4541	$91.45	$91.45	$91.50
Purchase #7	$76.38	7.446%	$82.0673	$82.07	$82.05	$82.10
7 purchase totals =	$1,031.13		$1,082.7217	$1,082.72	$1,082.75	$1,082.70