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	$229.70	9.538%	$251.6088	$251.61	$251.60	$251.60
Purchase #2	$134.50	6.619%	$143.4026	$143.40	$143.40	$143.40
Purchase #3	$7.92	5.764%	$8.3765	$8.38	$8.40	$8.40
Purchase #4	$58.95	10.605%	$65.2016	$65.20	$65.20	$65.20
Purchase #5	$180.67	4.864%	$189.4578	$189.46	$189.45	$189.50
Purchase #6	$65.42	10.746%	$72.45	$72.45	$72.45	$72.50
Purchase #7	$160.34	13.126%	$181.3862	$181.39	$181.40	$181.40
7 purchase totals =	$837.50		$911.8835	$911.89	$911.90	$912.00