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	$55.26	9.843%	$60.6992	$60.70	$60.70	$60.70
Purchase #2	$91.32	9.323%	$99.8338	$99.83	$99.85	$99.80
Purchase #3	$105.77	5.874%	$111.9829	$111.98	$112.00	$112.00
Purchase #4	$50.34	7.454%	$54.0923	$54.09	$54.10	$54.10
Purchase #5	$138.55	9.680%	$151.9616	$151.96	$151.95	$152.00
Purchase #6	$171.60	11.230%	$190.8707	$190.87	$190.85	$190.90
Purchase #7	$212.38	11.276%	$236.328	$236.33	$236.35	$236.30
7 purchase totals =	$825.22		$905.7685	$905.76	$905.80	$905.80