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	$220.86	5.428%	$232.8483	$232.85	$232.85	$232.80
Purchase #2	$188.28	9.222%	$205.6432	$205.64	$205.65	$205.60
Purchase #3	$34.86	13.406%	$39.5333	$39.53	$39.55	$39.50
Purchase #4	$89.37	3.244%	$92.2692	$92.27	$92.25	$92.30
Purchase #5	$7.94	8.728%	$8.633	$8.63	$8.65	$8.60
Purchase #6	$243.68	4.806%	$255.3913	$255.39	$255.40	$255.40
Purchase #7	$171.60	4.481%	$179.2894	$179.29	$179.30	$179.30
7 purchase totals =	$956.59		$1,013.6077	$1,013.60	$1,013.65	$1,013.50