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	$136.81	8.205%	$148.0353	$148.04	$148.05	$148.00
Purchase #2	$70.91	9.289%	$77.4968	$77.50	$77.50	$77.50
Purchase #3	$125.34	4.845%	$131.4127	$131.41	$131.40	$131.40
Purchase #4	$19.73	3.658%	$20.4517	$20.45	$20.45	$20.50
Purchase #5	$215.85	10.553%	$238.6287	$238.63	$238.65	$238.60
Purchase #6	$135.82	7.602%	$146.145	$146.15	$146.15	$146.10
Purchase #7	$125.98	10.565%	$139.2898	$139.29	$139.30	$139.30
7 purchase totals =	$830.44		$901.4600	$901.47	$901.50	$901.40