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	$83.90	9.516%	$91.8839	$91.88	$91.90	$91.90
Purchase #2	$143.69	5.599%	$151.7352	$151.74	$151.75	$151.70
Purchase #3	$214.61	12.836%	$242.1573	$242.16	$242.15	$242.20
Purchase #4	$74.46	8.354%	$80.6804	$80.68	$80.70	$80.70
Purchase #5	$217.86	4.207%	$227.0254	$227.03	$227.05	$227.00
Purchase #6	$83.32	7.867%	$89.8748	$89.87	$89.85	$89.90
Purchase #7	$159.71	7.705%	$172.0157	$172.02	$172.00	$172.00
7 purchase totals =	$977.55		$1,055.3727	$1,055.38	$1,055.40	$1,055.40