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	$187.40	12.278%	$210.409	$210.41	$210.40	$210.40
Purchase #2	$220.43	3.742%	$228.6785	$228.68	$228.70	$228.70
Purchase #3	$183.37	9.516%	$200.8195	$200.82	$200.80	$200.80
Purchase #4	$180.97	3.618%	$187.5175	$187.52	$187.50	$187.50
Purchase #5	$121.37	9.114%	$132.4317	$132.43	$132.45	$132.40
Purchase #6	$189.69	3.648%	$196.6099	$196.61	$196.60	$196.60
Purchase #7	$224.97	12.720%	$253.5862	$253.59	$253.60	$253.60
7 purchase totals =	$1,308.20		$1,410.0523	$1,410.06	$1,410.05	$1,410.00