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	$123.47	4.418%	$128.9249	$128.92	$128.90	$128.90
Purchase #2	$50.57	7.109%	$54.165	$54.17	$54.15	$54.20
Purchase #3	$143.51	7.169%	$153.7982	$153.80	$153.80	$153.80
Purchase #4	$92.82	11.448%	$103.446	$103.45	$103.45	$103.40
Purchase #5	$68.50	11.654%	$76.483	$76.48	$76.50	$76.50
Purchase #6	$70.38	9.836%	$77.3026	$77.30	$77.30	$77.30
Purchase #7	$107.93	9.171%	$117.8283	$117.83	$117.85	$117.80
7 purchase totals =	$657.18		$711.9480	$711.95	$711.95	$711.90