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	$233.48	11.717%	$260.8369	$260.84	$260.85	$260.80
Purchase #2	$94.62	5.767%	$100.0767	$100.08	$100.10	$100.10
Purchase #3	$119.81	11.292%	$133.3389	$133.34	$133.35	$133.30
Purchase #4	$101.87	7.811%	$109.8271	$109.83	$109.85	$109.80
Purchase #5	$197.36	6.450%	$210.0897	$210.09	$210.10	$210.10
Purchase #6	$102.63	8.638%	$111.4952	$111.50	$111.50	$111.50
Purchase #7	$34.83	13.269%	$39.4516	$39.45	$39.45	$39.50
7 purchase totals =	$884.60		$965.1161	$965.13	$965.20	$965.10