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	$221.37	5.507%	$233.5608	$233.56	$233.55	$233.60
Purchase #2	$136.52	5.369%	$143.8498	$143.85	$143.85	$143.80
Purchase #3	$170.82	11.418%	$190.3242	$190.32	$190.30	$190.30
Purchase #4	$94.93	13.780%	$108.0114	$108.01	$108.00	$108.00
Purchase #5	$247.72	9.861%	$272.1477	$272.15	$272.15	$272.10
Purchase #6	$98.68	4.290%	$102.9134	$102.91	$102.90	$102.90
Purchase #7	$22.26	10.501%	$24.5975	$24.60	$24.60	$24.60
7 purchase totals =	$992.30		$1,075.4048	$1,075.40	$1,075.35	$1,075.30