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	$160.27	7.531%	$172.3399	$172.34	$172.35	$172.30
Purchase #2	$154.57	10.651%	$171.0333	$171.03	$171.05	$171.00
Purchase #3	$62.40	13.526%	$70.8402	$70.84	$70.85	$70.80
Purchase #4	$32.38	6.831%	$34.5919	$34.59	$34.60	$34.60
Purchase #5	$119.49	13.364%	$135.4586	$135.46	$135.45	$135.50
Purchase #6	$31.73	4.511%	$33.1613	$33.16	$33.15	$33.20
Purchase #7	$100.91	3.602%	$104.5448	$104.54	$104.55	$104.50
7 purchase totals =	$661.75		$721.9700	$721.96	$722.00	$721.90