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	$52.55	11.132%	$58.3999	$58.40	$58.40	$58.40
Purchase #2	$105.52	8.506%	$114.4955	$114.50	$114.50	$114.50
Purchase #3	$75.48	4.356%	$78.7679	$78.77	$78.75	$78.80
Purchase #4	$50.82	4.561%	$53.1379	$53.14	$53.15	$53.10
Purchase #5	$50.85	4.378%	$53.0762	$53.08	$53.10	$53.10
Purchase #6	$135.68	7.799%	$146.2617	$146.26	$146.25	$146.30
Purchase #7	$48.33	11.338%	$53.8097	$53.81	$53.80	$53.80
7 purchase totals =	$519.23		$557.9488	$557.96	$557.95	$558.00