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	$48.28	10.452%	$53.3262	$53.33	$53.35	$53.30
Purchase #2	$70.65	8.753%	$76.834	$76.83	$76.85	$76.80
Purchase #3	$232.39	3.775%	$241.1627	$241.16	$241.15	$241.20
Purchase #4	$46.89	8.457%	$50.8555	$50.86	$50.85	$50.90
Purchase #5	$47.26	6.850%	$50.4973	$50.50	$50.50	$50.50
Purchase #6	$127.27	12.440%	$143.1024	$143.10	$143.10	$143.10
Purchase #7	$77.87	5.355%	$82.0399	$82.04	$82.05	$82.00
7 purchase totals =	$650.61		$697.8180	$697.82	$697.85	$697.80