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	$52.89	12.582%	$59.5446	$59.54	$59.55	$59.50
Purchase #2	$185.69	13.177%	$210.1584	$210.16	$210.15	$210.20
Purchase #3	$205.92	5.705%	$217.6677	$217.67	$217.65	$217.70
Purchase #4	$39.26	3.215%	$40.5222	$40.52	$40.50	$40.50
Purchase #5	$16.40	6.455%	$17.4586	$17.46	$17.45	$17.50
Purchase #6	$148.45	4.836%	$155.629	$155.63	$155.65	$155.60
Purchase #7	$242.45	10.271%	$267.352	$267.35	$267.35	$267.40
7 purchase totals =	$891.06		$968.3325	$968.33	$968.30	$968.40