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	$66.70	7.838%	$71.9279	$71.93	$71.95	$71.90
Purchase #2	$82.58	4.422%	$86.2317	$86.23	$86.25	$86.20
Purchase #3	$137.70	12.344%	$154.6977	$154.70	$154.70	$154.70
Purchase #4	$81.98	4.200%	$85.4232	$85.42	$85.40	$85.40
Purchase #5	$79.97	13.240%	$90.558	$90.56	$90.55	$90.60
Purchase #6	$21.45	4.653%	$22.4481	$22.45	$22.45	$22.40
Purchase #7	$144.97	12.294%	$162.7926	$162.79	$162.80	$162.80
7 purchase totals =	$615.35		$674.0792	$674.08	$674.10	$674.00