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	$51.34	6.128%	$54.4861	$54.49	$54.50	$54.50
Purchase #2	$201.47	6.196%	$213.9531	$213.95	$213.95	$214.00
Purchase #3	$102.91	8.374%	$111.5277	$111.53	$111.55	$111.50
Purchase #4	$122.88	4.315%	$128.1823	$128.18	$128.20	$128.20
Purchase #5	$224.28	7.824%	$241.8277	$241.83	$241.85	$241.80
Purchase #6	$92.71	12.853%	$104.626	$104.63	$104.65	$104.60
Purchase #7	$204.36	11.494%	$227.8491	$227.85	$227.85	$227.80
7 purchase totals =	$999.95		$1,082.4520	$1,082.46	$1,082.55	$1,082.40