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	$153.59	7.166%	$164.5963	$164.60	$164.60	$164.60
Purchase #2	$154.48	11.377%	$172.0552	$172.06	$172.05	$172.10
Purchase #3	$88.77	12.495%	$99.8618	$99.86	$99.85	$99.90
Purchase #4	$144.97	9.630%	$158.9306	$158.93	$158.95	$158.90
Purchase #5	$210.56	4.588%	$220.2205	$220.22	$220.20	$220.20
Purchase #6	$101.76	11.308%	$113.267	$113.27	$113.25	$113.30
Purchase #7	$217.63	9.177%	$237.6019	$237.60	$237.60	$237.60
7 purchase totals =	$1,071.76		$1,166.5333	$1,166.54	$1,166.50	$1,166.60