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	$230.83	6.516%	$245.8709	$245.87	$245.85	$245.90
Purchase #2	$54.70	13.407%	$62.0336	$62.03	$62.05	$62.00
Purchase #3	$112.69	3.203%	$116.2995	$116.30	$116.30	$116.30
Purchase #4	$64.29	11.752%	$71.8454	$71.85	$71.85	$71.80
Purchase #5	$191.29	8.705%	$207.9418	$207.94	$207.95	$207.90
Purchase #6	$199.91	7.594%	$215.0912	$215.09	$215.10	$215.10
Purchase #7	$40.50	7.362%	$43.4816	$43.48	$43.50	$43.50
7 purchase totals =	$894.21		$962.5640	$962.56	$962.60	$962.50