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	$239.93	8.498%	$260.3193	$260.32	$260.30	$260.30
Purchase #2	$47.36	8.411%	$51.3434	$51.34	$51.35	$51.30
Purchase #3	$173.31	13.166%	$196.128	$196.13	$196.15	$196.10
Purchase #4	$63.58	13.397%	$72.0978	$72.10	$72.10	$72.10
Purchase #5	$203.77	8.345%	$220.7746	$220.77	$220.75	$220.80
Purchase #6	$101.45	9.464%	$111.0512	$111.05	$111.05	$111.10
Purchase #7	$72.65	6.738%	$77.5452	$77.55	$77.55	$77.50
7 purchase totals =	$902.05		$989.2595	$989.26	$989.25	$989.20