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	$53.65	4.561%	$56.097	$56.10	$56.10	$56.10
Purchase #2	$142.84	5.206%	$150.2763	$150.28	$150.30	$150.30
Purchase #3	$76.26	3.397%	$78.8506	$78.85	$78.85	$78.90
Purchase #4	$241.56	11.513%	$269.3708	$269.37	$269.35	$269.40
Purchase #5	$174.52	10.214%	$192.3455	$192.35	$192.35	$192.30
Purchase #6	$119.58	3.248%	$123.464	$123.46	$123.45	$123.50
Purchase #7	$76.29	6.331%	$81.1199	$81.12	$81.10	$81.10
7 purchase totals =	$884.70		$951.5241	$951.53	$951.50	$951.60