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	$117.39	12.717%	$132.3185	$132.32	$132.30	$132.30
Purchase #2	$103.99	7.494%	$111.783	$111.78	$111.80	$111.80
Purchase #3	$103.57	11.654%	$115.64	$115.64	$115.65	$115.60
Purchase #4	$28.25	12.821%	$31.8719	$31.87	$31.85	$31.90
Purchase #5	$41.88	10.640%	$46.336	$46.34	$46.35	$46.30
Purchase #6	$113.96	11.659%	$127.2466	$127.25	$127.25	$127.20
Purchase #7	$76.43	13.652%	$86.8642	$86.86	$86.85	$86.90
7 purchase totals =	$585.47		$652.0602	$652.06	$652.05	$652.00