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	$156.51	9.606%	$171.5444	$171.54	$171.55	$171.50
Purchase #2	$98.71	13.429%	$111.9658	$111.97	$111.95	$112.00
Purchase #3	$188.37	9.613%	$206.478	$206.48	$206.50	$206.50
Purchase #4	$197.82	12.168%	$221.8907	$221.89	$221.90	$221.90
Purchase #5	$66.93	3.571%	$69.3201	$69.32	$69.30	$69.30
Purchase #6	$237.77	5.463%	$250.7594	$250.76	$250.75	$250.80
Purchase #7	$59.27	11.857%	$66.2976	$66.30	$66.30	$66.30
7 purchase totals =	$1,005.38		$1,098.2560	$1,098.26	$1,098.25	$1,098.30