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	$242.74	9.305%	$265.327	$265.33	$265.35	$265.30
Purchase #2	$169.29	7.169%	$181.4264	$181.43	$181.45	$181.40
Purchase #3	$203.37	9.510%	$222.7105	$222.71	$222.70	$222.70
Purchase #4	$166.30	3.591%	$172.2718	$172.27	$172.25	$172.30
Purchase #5	$104.26	5.363%	$109.8515	$109.85	$109.85	$109.90
Purchase #6	$45.43	6.457%	$48.3634	$48.36	$48.35	$48.40
Purchase #7	$11.87	7.309%	$12.7376	$12.74	$12.75	$12.70
7 purchase totals =	$943.26		$1,012.6882	$1,012.69	$1,012.70	$1,012.70