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	$89.80	6.798%	$95.9046	$95.90	$95.90	$95.90
Purchase #2	$79.85	13.487%	$90.6194	$90.62	$90.60	$90.60
Purchase #3	$180.81	11.648%	$201.8707	$201.87	$201.85	$201.90
Purchase #4	$238.71	6.169%	$253.436	$253.44	$253.45	$253.40
Purchase #5	$13.34	10.319%	$14.7166	$14.72	$14.70	$14.70
Purchase #6	$232.68	4.218%	$242.4944	$242.49	$242.50	$242.50
Purchase #7	$230.28	11.555%	$256.8889	$256.89	$256.90	$256.90
7 purchase totals =	$1,065.47		$1,155.9306	$1,155.93	$1,155.90	$1,155.90