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	$47.94	8.247%	$51.8936	$51.89	$51.90	$51.90
Purchase #2	$227.53	6.560%	$242.456	$242.46	$242.45	$242.50
Purchase #3	$61.46	4.511%	$64.2325	$64.23	$64.25	$64.20
Purchase #4	$81.89	4.733%	$85.7659	$85.77	$85.75	$85.80
Purchase #5	$171.46	8.249%	$185.6037	$185.60	$185.60	$185.60
Purchase #6	$137.62	10.337%	$151.8458	$151.85	$151.85	$151.80
Purchase #7	$119.30	5.520%	$125.8854	$125.89	$125.90	$125.90
7 purchase totals =	$847.20		$907.6829	$907.69	$907.70	$907.70