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	$59.43	12.576%	$66.9039	$66.90	$66.90	$66.90
Purchase #2	$111.34	11.480%	$124.1218	$124.12	$124.10	$124.10
Purchase #3	$148.78	12.629%	$167.5694	$167.57	$167.55	$167.60
Purchase #4	$149.98	5.385%	$158.0564	$158.06	$158.05	$158.10
Purchase #5	$206.76	10.792%	$229.0735	$229.07	$229.05	$229.10
Purchase #6	$47.55	12.263%	$53.3811	$53.38	$53.40	$53.40
Purchase #7	$176.32	4.738%	$184.674	$184.67	$184.65	$184.70
7 purchase totals =	$900.16		$983.7801	$983.77	$983.70	$983.90