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	$62.50	8.769%	$67.9806	$67.98	$68.00	$68.00
Purchase #2	$234.37	9.480%	$256.5883	$256.59	$256.60	$256.60
Purchase #3	$88.56	9.181%	$96.6907	$96.69	$96.70	$96.70
Purchase #4	$126.81	3.792%	$131.6186	$131.62	$131.60	$131.60
Purchase #5	$53.85	6.766%	$57.4935	$57.49	$57.50	$57.50
Purchase #6	$154.97	12.148%	$173.7958	$173.80	$173.80	$173.80
Purchase #7	$142.27	12.246%	$159.6924	$159.69	$159.70	$159.70
7 purchase totals =	$863.33		$943.8599	$943.86	$943.90	$943.90