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	$63.83	3.162%	$65.8483	$65.85	$65.85	$65.80
Purchase #2	$30.29	6.440%	$32.2407	$32.24	$32.25	$32.20
Purchase #3	$104.99	3.147%	$108.294	$108.29	$108.30	$108.30
Purchase #4	$99.58	12.495%	$112.0225	$112.02	$112.00	$112.00
Purchase #5	$164.27	10.372%	$181.3081	$181.31	$181.30	$181.30
Purchase #6	$20.69	6.689%	$22.074	$22.07	$22.05	$22.10
Purchase #7	$101.84	3.665%	$105.5724	$105.57	$105.55	$105.60
7 purchase totals =	$585.49		$627.3600	$627.35	$627.30	$627.30