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	$22.73	7.804%	$24.5038	$24.50	$24.50	$24.50
Purchase #2	$161.60	11.242%	$179.7671	$179.77	$179.75	$179.80
Purchase #3	$129.91	5.699%	$137.3136	$137.31	$137.30	$137.30
Purchase #4	$95.47	7.508%	$102.6379	$102.64	$102.65	$102.60
Purchase #5	$192.35	4.327%	$200.673	$200.67	$200.65	$200.70
Purchase #6	$172.65	3.550%	$178.7791	$178.78	$178.80	$178.80
Purchase #7	$167.96	10.204%	$185.0986	$185.10	$185.10	$185.10
7 purchase totals =	$942.67		$1,008.7731	$1,008.77	$1,008.75	$1,008.80