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	$75.52	8.698%	$82.0887	$82.09	$82.10	$82.10
Purchase #2	$83.91	12.732%	$94.5934	$94.59	$94.60	$94.60
Purchase #3	$57.98	9.544%	$63.5136	$63.51	$63.50	$63.50
Purchase #4	$222.95	12.406%	$250.6092	$250.61	$250.60	$250.60
Purchase #5	$54.75	13.840%	$62.3274	$62.33	$62.35	$62.30
Purchase #6	$198.86	9.282%	$217.3182	$217.32	$217.30	$217.30
Purchase #7	$81.49	12.675%	$91.8189	$91.82	$91.80	$91.80
7 purchase totals =	$775.46		$862.2694	$862.27	$862.25	$862.20