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	$176.30	6.122%	$187.0931	$187.09	$187.10	$187.10
Purchase #2	$143.72	8.215%	$155.5266	$155.53	$155.55	$155.50
Purchase #3	$205.38	8.765%	$223.3816	$223.38	$223.40	$223.40
Purchase #4	$208.94	11.692%	$233.3693	$233.37	$233.35	$233.40
Purchase #5	$121.50	9.316%	$132.8189	$132.82	$132.80	$132.80
Purchase #6	$75.54	3.684%	$78.3229	$78.32	$78.30	$78.30
Purchase #7	$47.56	3.317%	$49.1376	$49.14	$49.15	$49.10
7 purchase totals =	$978.94		$1,059.6500	$1,059.65	$1,059.65	$1,059.60