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	$197.94	4.256%	$206.3643	$206.36	$206.35	$206.40
Purchase #2	$76.56	11.673%	$85.4968	$85.50	$85.50	$85.50
Purchase #3	$70.30	13.176%	$79.5627	$79.56	$79.55	$79.60
Purchase #4	$29.69	7.603%	$31.9473	$31.95	$31.95	$31.90
Purchase #5	$75.41	9.361%	$82.4691	$82.47	$82.45	$82.50
Purchase #6	$102.45	13.305%	$116.081	$116.08	$116.10	$116.10
Purchase #7	$41.31	10.783%	$45.7645	$45.76	$45.75	$45.80
7 purchase totals =	$593.66		$647.6857	$647.68	$647.65	$647.80