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	$172.45	11.437%	$192.1731	$192.17	$192.15	$192.20
Purchase #2	$234.50	5.753%	$247.9908	$247.99	$248.00	$248.00
Purchase #3	$105.86	12.768%	$119.3762	$119.38	$119.40	$119.40
Purchase #4	$142.48	7.503%	$153.1703	$153.17	$153.15	$153.20
Purchase #5	$64.89	12.373%	$72.9188	$72.92	$72.90	$72.90
Purchase #6	$139.77	13.512%	$158.6557	$158.66	$158.65	$158.70
Purchase #7	$85.26	4.489%	$89.0873	$89.09	$89.10	$89.10
7 purchase totals =	$945.21		$1,033.3722	$1,033.38	$1,033.35	$1,033.50