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	$47.35	11.363%	$52.7304	$52.73	$52.75	$52.70
Purchase #2	$121.30	13.803%	$138.043	$138.04	$138.05	$138.00
Purchase #3	$247.56	4.228%	$258.0268	$258.03	$258.05	$258.00
Purchase #4	$151.82	8.290%	$164.4059	$164.41	$164.40	$164.40
Purchase #5	$18.35	11.759%	$20.5078	$20.51	$20.50	$20.50
Purchase #6	$43.69	11.700%	$48.8017	$48.80	$48.80	$48.80
Purchase #7	$40.85	6.546%	$43.524	$43.52	$43.50	$43.50
7 purchase totals =	$670.92		$726.0396	$726.04	$726.05	$725.90