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	$164.30	4.683%	$171.9942	$171.99	$172.00	$172.00
Purchase #2	$224.87	9.327%	$245.8436	$245.84	$245.85	$245.80
Purchase #3	$152.69	7.808%	$164.612	$164.61	$164.60	$164.60
Purchase #4	$173.27	10.387%	$191.2676	$191.27	$191.25	$191.30
Purchase #5	$44.47	5.385%	$46.8647	$46.86	$46.85	$46.90
Purchase #6	$110.74	5.572%	$116.9104	$116.91	$116.90	$116.90
Purchase #7	$198.72	13.395%	$225.3385	$225.34	$225.35	$225.30
7 purchase totals =	$1,069.06		$1,162.8310	$1,162.82	$1,162.80	$1,162.80