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	$145.30	13.822%	$165.3834	$165.38	$165.40	$165.40
Purchase #2	$19.41	9.371%	$21.2289	$21.23	$21.25	$21.20
Purchase #3	$54.76	8.661%	$59.5028	$59.50	$59.50	$59.50
Purchase #4	$139.55	13.689%	$158.653	$158.65	$158.65	$158.70
Purchase #5	$31.75	10.133%	$34.9672	$34.97	$34.95	$35.00
Purchase #6	$123.32	7.693%	$132.807	$132.81	$132.80	$132.80
Purchase #7	$213.52	4.417%	$222.9512	$222.95	$222.95	$223.00
7 purchase totals =	$727.61		$795.4935	$795.49	$795.50	$795.60