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	$118.28	4.687%	$123.8238	$123.82	$123.80	$123.80
Purchase #2	$45.54	3.429%	$47.1016	$47.10	$47.10	$47.10
Purchase #3	$130.50	4.280%	$136.0854	$136.09	$136.10	$136.10
Purchase #4	$31.56	9.439%	$34.5389	$34.54	$34.55	$34.50
Purchase #5	$223.86	8.390%	$242.6419	$242.64	$242.65	$242.60
Purchase #6	$199.91	10.116%	$220.1329	$220.13	$220.15	$220.10
Purchase #7	$191.45	7.572%	$205.9466	$205.95	$205.95	$205.90
7 purchase totals =	$941.10		$1,010.2711	$1,010.27	$1,010.30	$1,010.10