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	$85.78	12.622%	$96.6072	$96.61	$96.60	$96.60
Purchase #2	$187.97	4.634%	$196.6805	$196.68	$196.70	$196.70
Purchase #3	$73.61	10.143%	$81.0763	$81.08	$81.10	$81.10
Purchase #4	$124.33	10.855%	$137.826	$137.83	$137.85	$137.80
Purchase #5	$6.69	8.658%	$7.2692	$7.27	$7.25	$7.30
Purchase #6	$49.78	10.316%	$54.9153	$54.92	$54.90	$54.90
Purchase #7	$119.77	8.831%	$130.3469	$130.35	$130.35	$130.30
7 purchase totals =	$647.93		$704.7214	$704.74	$704.75	$704.70