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	$124.52	7.389%	$133.7208	$133.72	$133.70	$133.70
Purchase #2	$122.64	6.825%	$131.0102	$131.01	$131.00	$131.00
Purchase #3	$46.62	5.451%	$49.1613	$49.16	$49.15	$49.20
Purchase #4	$191.61	11.579%	$213.7965	$213.80	$213.80	$213.80
Purchase #5	$118.32	7.856%	$127.6152	$127.62	$127.60	$127.60
Purchase #6	$27.42	4.796%	$28.7351	$28.74	$28.75	$28.70
Purchase #7	$117.98	11.494%	$131.5406	$131.54	$131.55	$131.50
7 purchase totals =	$749.11		$815.5797	$815.59	$815.55	$815.50