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	$168.46	3.258%	$173.9484	$173.95	$173.95	$173.90
Purchase #2	$114.38	8.244%	$123.8095	$123.81	$123.80	$123.80
Purchase #3	$10.99	10.318%	$12.1239	$12.12	$12.10	$12.10
Purchase #4	$39.78	6.714%	$42.4508	$42.45	$42.45	$42.50
Purchase #5	$74.94	8.399%	$81.2342	$81.23	$81.25	$81.20
Purchase #6	$38.61	11.504%	$43.0517	$43.05	$43.05	$43.10
Purchase #7	$144.96	7.819%	$156.2944	$156.29	$156.30	$156.30
7 purchase totals =	$592.12		$632.9129	$632.90	$632.90	$632.90