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	$52.37	4.141%	$54.5386	$54.54	$54.55	$54.50
Purchase #2	$17.40	5.217%	$18.3078	$18.31	$18.30	$18.30
Purchase #3	$34.95	4.550%	$36.5402	$36.54	$36.55	$36.50
Purchase #4	$219.56	8.786%	$238.8505	$238.85	$238.85	$238.90
Purchase #5	$18.45	3.209%	$19.0421	$19.04	$19.05	$19.00
Purchase #6	$74.69	3.818%	$77.5417	$77.54	$77.55	$77.50
Purchase #7	$9.74	7.393%	$10.4601	$10.46	$10.45	$10.50
7 purchase totals =	$427.16		$455.2810	$455.28	$455.30	$455.20