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	$145.59	7.498%	$156.5063	$156.51	$156.50	$156.50
Purchase #2	$137.94	12.806%	$155.6046	$155.60	$155.60	$155.60
Purchase #3	$185.42	8.110%	$200.4576	$200.46	$200.45	$200.50
Purchase #4	$159.56	3.704%	$165.4701	$165.47	$165.45	$165.50
Purchase #5	$222.75	5.445%	$234.8787	$234.88	$234.90	$234.90
Purchase #6	$138.47	5.800%	$146.5013	$146.50	$146.50	$146.50
Purchase #7	$76.94	7.367%	$82.6082	$82.61	$82.60	$82.60
7 purchase totals =	$1,066.67		$1,142.0268	$1,142.03	$1,142.00	$1,142.10