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	$173.89	4.250%	$181.2803	$181.28	$181.30	$181.30
Purchase #2	$127.62	10.246%	$140.6959	$140.70	$140.70	$140.70
Purchase #3	$161.55	4.505%	$168.8278	$168.83	$168.85	$168.80
Purchase #4	$211.61	5.564%	$223.384	$223.38	$223.40	$223.40
Purchase #5	$49.41	3.830%	$51.3024	$51.30	$51.30	$51.30
Purchase #6	$143.34	8.715%	$155.8321	$155.83	$155.85	$155.80
Purchase #7	$86.68	6.318%	$92.1564	$92.16	$92.15	$92.20
7 purchase totals =	$954.10		$1,013.4789	$1,013.48	$1,013.55	$1,013.50