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	$156.70	7.141%	$167.8899	$167.89	$167.90	$167.90
Purchase #2	$148.78	4.380%	$155.2966	$155.30	$155.30	$155.30
Purchase #3	$136.87	9.201%	$149.4634	$149.46	$149.45	$149.50
Purchase #4	$21.65	3.820%	$22.477	$22.48	$22.50	$22.50
Purchase #5	$109.46	3.354%	$113.1313	$113.13	$113.15	$113.10
Purchase #6	$200.71	9.158%	$219.091	$219.09	$219.10	$219.10
Purchase #7	$242.82	5.783%	$256.8623	$256.86	$256.85	$256.90
7 purchase totals =	$1,016.99		$1,084.2115	$1,084.21	$1,084.25	$1,084.30