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	$54.46	13.715%	$61.9292	$61.93	$61.95	$61.90
Purchase #2	$36.43	8.310%	$39.4573	$39.46	$39.45	$39.50
Purchase #3	$150.49	10.473%	$166.2508	$166.25	$166.25	$166.30
Purchase #4	$133.73	5.722%	$141.382	$141.38	$141.40	$141.40
Purchase #5	$168.97	12.346%	$189.831	$189.83	$189.85	$189.80
Purchase #6	$89.65	12.687%	$101.0239	$101.02	$101.00	$101.00
Purchase #7	$118.31	7.852%	$127.5997	$127.60	$127.60	$127.60
7 purchase totals =	$752.04		$827.4739	$827.47	$827.50	$827.50