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	$15.99	11.625%	$17.8488	$17.85	$17.85	$17.80
Purchase #2	$70.85	10.171%	$78.0562	$78.06	$78.05	$78.10
Purchase #3	$36.51	4.789%	$38.2585	$38.26	$38.25	$38.30
Purchase #4	$227.29	11.429%	$253.267	$253.27	$253.25	$253.30
Purchase #5	$58.99	10.339%	$65.089	$65.09	$65.10	$65.10
Purchase #6	$243.49	11.111%	$270.5442	$270.54	$270.55	$270.50
Purchase #7	$206.30	7.377%	$221.5188	$221.52	$221.50	$221.50
7 purchase totals =	$859.42		$944.5825	$944.59	$944.55	$944.60