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	$67.61	9.515%	$74.0431	$74.04	$74.05	$74.00
Purchase #2	$187.73	7.311%	$201.4549	$201.45	$201.45	$201.50
Purchase #3	$171.82	5.704%	$181.6206	$181.62	$181.60	$181.60
Purchase #4	$140.38	9.501%	$153.7175	$153.72	$153.70	$153.70
Purchase #5	$111.88	13.510%	$126.995	$127.00	$127.00	$127.00
Purchase #6	$74.70	4.789%	$78.2774	$78.28	$78.30	$78.30
Purchase #7	$33.83	11.594%	$37.7523	$37.75	$37.75	$37.80
7 purchase totals =	$787.95		$853.8608	$853.86	$853.85	$853.90