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	$204.85	12.440%	$230.3333	$230.33	$230.35	$230.30
Purchase #2	$161.51	10.753%	$178.8772	$178.88	$178.90	$178.90
Purchase #3	$117.85	6.861%	$125.9357	$125.94	$125.95	$125.90
Purchase #4	$44.33	3.635%	$45.9414	$45.94	$45.95	$45.90
Purchase #5	$218.55	9.140%	$238.5255	$238.53	$238.55	$238.50
Purchase #6	$103.28	13.590%	$117.3158	$117.32	$117.30	$117.30
Purchase #7	$232.95	9.820%	$255.8257	$255.83	$255.85	$255.80
7 purchase totals =	$1,083.32		$1,192.7546	$1,192.77	$1,192.85	$1,192.60