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	$164.33	13.777%	$186.9697	$186.97	$186.95	$187.00
Purchase #2	$138.54	4.454%	$144.7106	$144.71	$144.70	$144.70
Purchase #3	$92.45	6.275%	$98.2512	$98.25	$98.25	$98.30
Purchase #4	$232.61	3.765%	$241.3678	$241.37	$241.35	$241.40
Purchase #5	$195.83	10.602%	$216.5919	$216.59	$216.60	$216.60
Purchase #6	$155.43	10.352%	$171.5201	$171.52	$171.50	$171.50
Purchase #7	$6.82	3.377%	$7.0503	$7.05	$7.05	$7.10
7 purchase totals =	$986.01		$1,066.4616	$1,066.46	$1,066.40	$1,066.60