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	$65.65	13.667%	$74.6224	$74.62	$74.60	$74.60
Purchase #2	$6.72	4.415%	$7.0167	$7.02	$7.00	$7.00
Purchase #3	$76.78	8.665%	$83.433	$83.43	$83.45	$83.40
Purchase #4	$80.31	6.660%	$85.6586	$85.66	$85.65	$85.70
Purchase #5	$77.54	4.822%	$81.279	$81.28	$81.30	$81.30
Purchase #6	$127.64	13.128%	$144.3966	$144.40	$144.40	$144.40
Purchase #7	$141.41	8.194%	$152.9971	$153.00	$153.00	$153.00
7 purchase totals =	$576.05		$629.4034	$629.41	$629.40	$629.40