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	$181.64	9.244%	$198.4308	$198.43	$198.45	$198.40
Purchase #2	$69.59	13.283%	$78.8336	$78.83	$78.85	$78.80
Purchase #3	$195.36	7.107%	$209.2442	$209.24	$209.25	$209.20
Purchase #4	$150.65	9.583%	$165.0868	$165.09	$165.10	$165.10
Purchase #5	$170.28	9.523%	$186.4958	$186.50	$186.50	$186.50
Purchase #6	$245.60	13.836%	$279.5812	$279.58	$279.60	$279.60
Purchase #7	$60.80	9.461%	$66.5523	$66.55	$66.55	$66.60
7 purchase totals =	$1,073.92		$1,184.2247	$1,184.22	$1,184.30	$1,184.20