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	$148.40	7.395%	$159.3742	$159.37	$159.35	$159.40
Purchase #2	$164.51	8.728%	$178.8684	$178.87	$178.85	$178.90
Purchase #3	$225.82	12.621%	$254.3207	$254.32	$254.30	$254.30
Purchase #4	$156.94	5.798%	$166.0394	$166.04	$166.05	$166.00
Purchase #5	$50.78	7.126%	$54.3986	$54.40	$54.40	$54.40
Purchase #6	$40.80	6.650%	$43.5132	$43.51	$43.50	$43.50
Purchase #7	$91.35	5.631%	$96.4939	$96.49	$96.50	$96.50
7 purchase totals =	$878.60		$953.0084	$953.00	$952.95	$953.00