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	$70.25	13.129%	$79.4731	$79.47	$79.45	$79.50
Purchase #2	$169.96	6.850%	$181.6023	$181.60	$181.60	$181.60
Purchase #3	$56.26	8.412%	$60.9926	$60.99	$61.00	$61.00
Purchase #4	$185.28	12.545%	$208.5234	$208.52	$208.50	$208.50
Purchase #5	$151.39	13.566%	$171.9276	$171.93	$171.95	$171.90
Purchase #6	$70.47	11.470%	$78.5529	$78.55	$78.55	$78.60
Purchase #7	$234.64	9.207%	$256.2433	$256.24	$256.25	$256.20
7 purchase totals =	$938.25		$1,037.3152	$1,037.30	$1,037.30	$1,037.30