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	$184.43	3.453%	$190.7984	$190.80	$190.80	$190.80
Purchase #2	$50.45	3.681%	$52.3071	$52.31	$52.30	$52.30
Purchase #3	$25.72	7.169%	$27.5639	$27.56	$27.55	$27.60
Purchase #4	$66.70	7.721%	$71.8499	$71.85	$71.85	$71.80
Purchase #5	$34.59	7.418%	$37.1559	$37.16	$37.15	$37.20
Purchase #6	$41.63	13.678%	$47.3242	$47.32	$47.30	$47.30
Purchase #7	$135.50	13.638%	$153.9795	$153.98	$154.00	$154.00
7 purchase totals =	$539.02		$580.9789	$580.98	$580.95	$581.00