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	$44.31	11.479%	$49.3963	$49.40	$49.40	$49.40
Purchase #2	$55.87	10.206%	$61.5721	$61.57	$61.55	$61.60
Purchase #3	$115.43	10.159%	$127.1565	$127.16	$127.15	$127.20
Purchase #4	$138.80	7.241%	$148.8505	$148.85	$148.85	$148.90
Purchase #5	$217.28	5.650%	$229.5563	$229.56	$229.55	$229.60
Purchase #6	$200.64	12.317%	$225.3528	$225.35	$225.35	$225.40
Purchase #7	$54.80	10.490%	$60.5485	$60.55	$60.55	$60.50
7 purchase totals =	$827.13		$902.4330	$902.44	$902.40	$902.60