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	$98.48	8.479%	$106.8301	$106.83	$106.85	$106.80
Purchase #2	$108.38	13.831%	$123.37	$123.37	$123.35	$123.40
Purchase #3	$54.37	12.198%	$61.0021	$61.00	$61.00	$61.00
Purchase #4	$26.41	3.414%	$27.3116	$27.31	$27.30	$27.30
Purchase #5	$246.61	10.612%	$272.7803	$272.78	$272.80	$272.80
Purchase #6	$20.68	4.311%	$21.5715	$21.57	$21.55	$21.60
Purchase #7	$20.52	11.464%	$22.8724	$22.87	$22.85	$22.90
7 purchase totals =	$575.45		$635.7380	$635.73	$635.70	$635.80