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	$86.73	4.274%	$90.4368	$90.44	$90.45	$90.40
Purchase #2	$121.88	4.853%	$127.7948	$127.79	$127.80	$127.80
Purchase #3	$116.44	5.543%	$122.8943	$122.89	$122.90	$122.90
Purchase #4	$181.73	8.684%	$197.5114	$197.51	$197.50	$197.50
Purchase #5	$109.98	3.540%	$113.8733	$113.87	$113.85	$113.90
Purchase #6	$166.38	10.748%	$184.2625	$184.26	$184.25	$184.30
Purchase #7	$195.35	8.798%	$212.5369	$212.54	$212.55	$212.50
7 purchase totals =	$978.49		$1,049.3100	$1,049.30	$1,049.30	$1,049.30