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	$108.63	5.455%	$114.5558	$114.56	$114.55	$114.60
Purchase #2	$72.27	7.218%	$77.4864	$77.49	$77.50	$77.50
Purchase #3	$89.37	9.296%	$97.6778	$97.68	$97.70	$97.70
Purchase #4	$100.25	9.514%	$109.7878	$109.79	$109.80	$109.80
Purchase #5	$104.34	11.540%	$116.3808	$116.38	$116.40	$116.40
Purchase #6	$28.39	3.712%	$29.4438	$29.44	$29.45	$29.40
Purchase #7	$194.98	11.853%	$218.091	$218.09	$218.10	$218.10
7 purchase totals =	$698.23		$763.4234	$763.43	$763.50	$763.50