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	$217.33	5.109%	$228.4334	$228.43	$228.45	$228.40
Purchase #2	$80.80	3.412%	$83.5569	$83.56	$83.55	$83.60
Purchase #3	$154.72	11.210%	$172.0641	$172.06	$172.05	$172.10
Purchase #4	$187.48	12.151%	$210.2607	$210.26	$210.25	$210.30
Purchase #5	$79.60	11.684%	$88.9005	$88.90	$88.90	$88.90
Purchase #6	$144.80	12.307%	$162.6205	$162.62	$162.60	$162.60
Purchase #7	$139.50	8.862%	$151.8625	$151.86	$151.85	$151.90
7 purchase totals =	$1,004.23		$1,097.6986	$1,097.69	$1,097.65	$1,097.80