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	$44.28	11.323%	$49.2938	$49.29	$49.30	$49.30
Purchase #2	$155.72	11.276%	$173.279	$173.28	$173.30	$173.30
Purchase #3	$75.58	4.406%	$78.9101	$78.91	$78.90	$78.90
Purchase #4	$113.82	10.307%	$125.5514	$125.55	$125.55	$125.60
Purchase #5	$40.90	6.282%	$43.4693	$43.47	$43.45	$43.50
Purchase #6	$115.45	13.435%	$130.9607	$130.96	$130.95	$131.00
Purchase #7	$102.26	7.445%	$109.8733	$109.87	$109.85	$109.90
7 purchase totals =	$648.01		$711.3376	$711.33	$711.30	$711.50