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	$150.43	4.597%	$157.3453	$157.35	$157.35	$157.30
Purchase #2	$207.67	8.102%	$224.4954	$224.50	$224.50	$224.50
Purchase #3	$24.88	13.845%	$28.3246	$28.32	$28.30	$28.30
Purchase #4	$56.72	4.436%	$59.2361	$59.24	$59.25	$59.20
Purchase #5	$50.25	4.168%	$52.3444	$52.34	$52.35	$52.30
Purchase #6	$105.95	12.391%	$119.0783	$119.08	$119.10	$119.10
Purchase #7	$151.96	13.723%	$172.8135	$172.81	$172.80	$172.80
7 purchase totals =	$747.86		$813.6376	$813.64	$813.65	$813.50