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	$49.57	4.318%	$51.7104	$51.71	$51.70	$51.70
Purchase #2	$14.93	12.287%	$16.7644	$16.76	$16.75	$16.80
Purchase #3	$184.86	6.140%	$196.2104	$196.21	$196.20	$196.20
Purchase #4	$105.30	5.752%	$111.3569	$111.36	$111.35	$111.40
Purchase #5	$55.57	7.466%	$59.7189	$59.72	$59.70	$59.70
Purchase #6	$223.48	3.403%	$231.085	$231.09	$231.10	$231.10
Purchase #7	$72.40	10.222%	$79.8007	$79.80	$79.80	$79.80
7 purchase totals =	$706.11		$746.6467	$746.65	$746.60	$746.70