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	$43.70	6.678%	$46.6183	$46.62	$46.60	$46.60
Purchase #2	$40.36	6.487%	$42.9782	$42.98	$43.00	$43.00
Purchase #3	$233.60	6.217%	$248.1229	$248.12	$248.10	$248.10
Purchase #4	$156.58	11.828%	$175.1003	$175.10	$175.10	$175.10
Purchase #5	$105.58	5.646%	$111.541	$111.54	$111.55	$111.50
Purchase #6	$93.40	13.162%	$105.6933	$105.69	$105.70	$105.70
Purchase #7	$239.41	10.816%	$265.3046	$265.30	$265.30	$265.30
7 purchase totals =	$912.63		$995.3586	$995.35	$995.35	$995.30