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	$242.36	11.151%	$269.3856	$269.39	$269.40	$269.40
Purchase #2	$45.72	6.860%	$48.8564	$48.86	$48.85	$48.90
Purchase #3	$105.60	3.113%	$108.8873	$108.89	$108.90	$108.90
Purchase #4	$27.90	5.598%	$29.4618	$29.46	$29.45	$29.50
Purchase #5	$161.49	5.840%	$170.921	$170.92	$170.90	$170.90
Purchase #6	$92.80	11.173%	$103.1685	$103.17	$103.15	$103.20
Purchase #7	$196.98	7.282%	$211.3241	$211.32	$211.30	$211.30
7 purchase totals =	$872.85		$942.0047	$942.01	$941.95	$942.10