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	$29.98	12.814%	$33.8216	$33.82	$33.80	$33.80
Purchase #2	$249.85	5.401%	$263.3444	$263.34	$263.35	$263.30
Purchase #3	$143.96	6.189%	$152.8697	$152.87	$152.85	$152.90
Purchase #4	$159.37	9.146%	$173.946	$173.95	$173.95	$173.90
Purchase #5	$148.49	10.874%	$164.6368	$164.64	$164.65	$164.60
Purchase #6	$89.88	10.637%	$99.4405	$99.44	$99.45	$99.40
Purchase #7	$118.39	3.595%	$122.6461	$122.65	$122.65	$122.60
7 purchase totals =	$939.92		$1,010.7051	$1,010.71	$1,010.70	$1,010.50