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	$33.93	10.238%	$37.4038	$37.40	$37.40	$37.40
Purchase #2	$248.35	5.821%	$262.8065	$262.81	$262.80	$262.80
Purchase #3	$96.52	9.553%	$105.7406	$105.74	$105.75	$105.70
Purchase #4	$113.32	4.195%	$118.0738	$118.07	$118.05	$118.10
Purchase #5	$226.66	9.666%	$248.569	$248.57	$248.55	$248.60
Purchase #6	$204.57	9.470%	$223.9428	$223.94	$223.95	$223.90
Purchase #7	$81.89	11.671%	$91.4474	$91.45	$91.45	$91.40
7 purchase totals =	$1,005.24		$1,087.9839	$1,087.98	$1,087.95	$1,087.90