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	$26.47	8.850%	$28.8126	$28.81	$28.80	$28.80
Purchase #2	$25.68	10.657%	$28.4167	$28.42	$28.40	$28.40
Purchase #3	$67.85	6.632%	$72.3498	$72.35	$72.35	$72.30
Purchase #4	$236.66	11.386%	$263.6061	$263.61	$263.60	$263.60
Purchase #5	$28.52	13.857%	$32.472	$32.47	$32.45	$32.50
Purchase #6	$210.80	7.201%	$225.9797	$225.98	$226.00	$226.00
Purchase #7	$180.35	10.716%	$199.6763	$199.68	$199.70	$199.70
7 purchase totals =	$776.33		$851.3132	$851.32	$851.30	$851.30