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	$212.59	7.180%	$227.854	$227.85	$227.85	$227.90
Purchase #2	$106.30	9.816%	$116.7344	$116.73	$116.75	$116.70
Purchase #3	$62.53	4.745%	$65.497	$65.50	$65.50	$65.50
Purchase #4	$109.50	8.617%	$118.9356	$118.94	$118.95	$118.90
Purchase #5	$85.41	6.181%	$90.6892	$90.69	$90.70	$90.70
Purchase #6	$148.33	12.573%	$166.9795	$166.98	$167.00	$167.00
Purchase #7	$82.85	13.699%	$94.1996	$94.20	$94.20	$94.20
7 purchase totals =	$807.51		$880.8893	$880.89	$880.95	$880.90