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	$88.93	9.450%	$97.3339	$97.33	$97.35	$97.30
Purchase #2	$58.26	6.501%	$62.0475	$62.05	$62.05	$62.00
Purchase #3	$167.34	12.307%	$187.9345	$187.93	$187.95	$187.90
Purchase #4	$99.95	11.756%	$111.7001	$111.70	$111.70	$111.70
Purchase #5	$242.77	8.360%	$263.0656	$263.07	$263.05	$263.10
Purchase #6	$176.75	11.201%	$196.5478	$196.55	$196.55	$196.50
Purchase #7	$93.56	7.687%	$100.752	$100.75	$100.75	$100.80
7 purchase totals =	$927.56		$1,019.3814	$1,019.38	$1,019.40	$1,019.30