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	$164.81	7.359%	$176.9384	$176.94	$176.95	$176.90
Purchase #2	$96.49	4.627%	$100.9546	$100.95	$100.95	$101.00
Purchase #3	$173.79	9.668%	$190.592	$190.59	$190.60	$190.60
Purchase #4	$223.78	8.446%	$242.6805	$242.68	$242.70	$242.70
Purchase #5	$52.57	3.737%	$54.5345	$54.53	$54.55	$54.50
Purchase #6	$119.91	9.282%	$131.04	$131.04	$131.05	$131.00
Purchase #7	$79.39	13.386%	$90.0171	$90.02	$90.00	$90.00
7 purchase totals =	$910.74		$986.7571	$986.75	$986.80	$986.70