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	$41.39	13.119%	$46.82	$46.82	$46.80	$46.80
Purchase #2	$111.55	4.370%	$116.4247	$116.42	$116.40	$116.40
Purchase #3	$12.57	3.439%	$13.0023	$13.00	$13.00	$13.00
Purchase #4	$229.69	12.462%	$258.314	$258.31	$258.30	$258.30
Purchase #5	$47.99	6.581%	$51.1482	$51.15	$51.15	$51.10
Purchase #6	$135.32	11.114%	$150.3595	$150.36	$150.35	$150.40
Purchase #7	$193.53	9.776%	$212.4495	$212.45	$212.45	$212.40
7 purchase totals =	$772.04		$848.5182	$848.51	$848.45	$848.40