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	$46.32	4.342%	$48.3312	$48.33	$48.35	$48.30
Purchase #2	$89.59	11.354%	$99.762	$99.76	$99.75	$99.80
Purchase #3	$97.39	13.802%	$110.8318	$110.83	$110.85	$110.80
Purchase #4	$42.75	6.239%	$45.4172	$45.42	$45.40	$45.40
Purchase #5	$211.93	11.452%	$236.2002	$236.20	$236.20	$236.20
Purchase #6	$185.86	9.566%	$203.6394	$203.64	$203.65	$203.60
Purchase #7	$242.56	5.390%	$255.634	$255.63	$255.65	$255.60
7 purchase totals =	$916.40		$999.8158	$999.81	$999.85	$999.70