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	$140.51	8.536%	$152.5039	$152.50	$152.50	$152.50
Purchase #2	$152.75	4.456%	$159.5565	$159.56	$159.55	$159.60
Purchase #3	$161.46	4.352%	$168.4867	$168.49	$168.50	$168.50
Purchase #4	$19.31	6.800%	$20.6231	$20.62	$20.60	$20.60
Purchase #5	$195.56	13.699%	$222.3498	$222.35	$222.35	$222.30
Purchase #6	$161.82	4.484%	$169.076	$169.08	$169.10	$169.10
Purchase #7	$155.29	12.306%	$174.4	$174.40	$174.40	$174.40
7 purchase totals =	$986.70		$1,066.9960	$1,067.00	$1,067.00	$1,067.00