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	$98.56	7.379%	$105.8327	$105.83	$105.85	$105.80
Purchase #2	$228.52	5.536%	$241.1709	$241.17	$241.15	$241.20
Purchase #3	$249.89	5.366%	$263.2991	$263.30	$263.30	$263.30
Purchase #4	$71.78	12.709%	$80.9025	$80.90	$80.90	$80.90
Purchase #5	$151.64	6.307%	$161.2039	$161.20	$161.20	$161.20
Purchase #6	$113.71	6.739%	$121.3729	$121.37	$121.35	$121.40
Purchase #7	$26.54	11.748%	$29.6579	$29.66	$29.65	$29.70
7 purchase totals =	$940.64		$1,003.4399	$1,003.43	$1,003.40	$1,003.50