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	$109.49	13.818%	$124.6193	$124.62	$124.60	$124.60
Purchase #2	$157.64	6.314%	$167.5934	$167.59	$167.60	$167.60
Purchase #3	$10.27	4.731%	$10.7559	$10.76	$10.75	$10.80
Purchase #4	$179.52	6.231%	$190.7059	$190.71	$190.70	$190.70
Purchase #5	$141.76	11.604%	$158.2098	$158.21	$158.20	$158.20
Purchase #6	$139.60	11.814%	$156.0923	$156.09	$156.10	$156.10
Purchase #7	$24.74	9.213%	$27.0193	$27.02	$27.00	$27.00
7 purchase totals =	$763.02		$834.9959	$835.00	$834.95	$835.00