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	$210.56	8.552%	$228.5671	$228.57	$228.55	$228.60
Purchase #2	$102.83	8.836%	$111.9161	$111.92	$111.90	$111.90
Purchase #3	$80.81	10.680%	$89.4405	$89.44	$89.45	$89.40
Purchase #4	$9.66	10.729%	$10.6964	$10.70	$10.70	$10.70
Purchase #5	$161.93	5.871%	$171.4369	$171.44	$171.45	$171.40
Purchase #6	$233.63	10.567%	$258.3177	$258.32	$258.30	$258.30
Purchase #7	$219.85	12.388%	$247.085	$247.09	$247.10	$247.10
7 purchase totals =	$1,019.27		$1,117.4597	$1,117.48	$1,117.45	$1,117.40