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	$167.54	6.277%	$178.0565	$178.06	$178.05	$178.10
Purchase #2	$164.32	8.679%	$178.5813	$178.58	$178.60	$178.60
Purchase #3	$36.36	4.215%	$37.8926	$37.89	$37.90	$37.90
Purchase #4	$90.85	5.142%	$95.5215	$95.52	$95.50	$95.50
Purchase #5	$39.25	4.398%	$40.9762	$40.98	$41.00	$41.00
Purchase #6	$29.53	8.211%	$31.9547	$31.95	$31.95	$32.00
Purchase #7	$14.63	6.596%	$15.595	$15.60	$15.60	$15.60
7 purchase totals =	$542.48		$578.5778	$578.58	$578.60	$578.70