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	$241.71	3.549%	$250.2883	$250.29	$250.30	$250.30
Purchase #2	$10.69	8.872%	$11.6384	$11.64	$11.65	$11.60
Purchase #3	$127.91	10.856%	$141.7959	$141.80	$141.80	$141.80
Purchase #4	$174.29	9.436%	$190.736	$190.74	$190.75	$190.70
Purchase #5	$166.41	9.262%	$181.8229	$181.82	$181.80	$181.80
Purchase #6	$83.30	8.448%	$90.3372	$90.34	$90.35	$90.30
Purchase #7	$223.86	4.874%	$234.7709	$234.77	$234.75	$234.80
7 purchase totals =	$1,028.17		$1,101.3896	$1,101.40	$1,101.40	$1,101.30