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	$104.28	6.487%	$111.0446	$111.04	$111.05	$111.00
Purchase #2	$15.96	4.794%	$16.7251	$16.73	$16.75	$16.70
Purchase #3	$47.93	13.654%	$54.4744	$54.47	$54.45	$54.50
Purchase #4	$213.47	8.752%	$232.1529	$232.15	$232.15	$232.20
Purchase #5	$186.29	7.615%	$200.476	$200.48	$200.50	$200.50
Purchase #6	$94.44	6.461%	$100.5418	$100.54	$100.55	$100.50
Purchase #7	$228.33	11.769%	$255.2022	$255.20	$255.20	$255.20
7 purchase totals =	$890.70		$970.6170	$970.61	$970.65	$970.60