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	$184.82	6.510%	$196.8518	$196.85	$196.85	$196.90
Purchase #2	$19.43	4.189%	$20.2439	$20.24	$20.25	$20.20
Purchase #3	$245.74	7.618%	$264.4605	$264.46	$264.45	$264.50
Purchase #4	$73.50	3.617%	$76.1585	$76.16	$76.15	$76.20
Purchase #5	$72.38	6.700%	$77.2295	$77.23	$77.25	$77.20
Purchase #6	$231.40	10.196%	$254.9935	$254.99	$255.00	$255.00
Purchase #7	$222.50	3.522%	$230.3365	$230.34	$230.35	$230.30
7 purchase totals =	$1,049.77		$1,120.2742	$1,120.27	$1,120.30	$1,120.30