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	$144.70	8.681%	$157.2614	$157.26	$157.25	$157.30
Purchase #2	$160.42	11.722%	$179.2244	$179.22	$179.20	$179.20
Purchase #3	$138.69	13.160%	$156.9416	$156.94	$156.95	$156.90
Purchase #4	$34.75	13.203%	$39.338	$39.34	$39.35	$39.30
Purchase #5	$196.44	8.154%	$212.4577	$212.46	$212.45	$212.50
Purchase #6	$153.68	10.728%	$170.1668	$170.17	$170.15	$170.20
Purchase #7	$249.84	12.425%	$280.8826	$280.88	$280.90	$280.90
7 purchase totals =	$1,078.52		$1,196.2725	$1,196.27	$1,196.25	$1,196.30