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	$69.27	13.344%	$78.5134	$78.51	$78.50	$78.50
Purchase #2	$79.93	8.572%	$86.7816	$86.78	$86.80	$86.80
Purchase #3	$168.48	8.227%	$182.3408	$182.34	$182.35	$182.30
Purchase #4	$203.46	13.461%	$230.8478	$230.85	$230.85	$230.80
Purchase #5	$153.40	3.518%	$158.7966	$158.80	$158.80	$158.80
Purchase #6	$138.66	9.762%	$152.196	$152.20	$152.20	$152.20
Purchase #7	$211.27	12.558%	$237.8013	$237.80	$237.80	$237.80
7 purchase totals =	$1,024.47		$1,127.2775	$1,127.28	$1,127.30	$1,127.20