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	$199.53	11.107%	$221.6918	$221.69	$221.70	$221.70
Purchase #2	$156.40	10.796%	$173.2849	$173.28	$173.30	$173.30
Purchase #3	$198.83	13.491%	$225.6542	$225.65	$225.65	$225.70
Purchase #4	$158.25	10.399%	$174.7064	$174.71	$174.70	$174.70
Purchase #5	$113.88	12.623%	$128.2551	$128.26	$128.25	$128.30
Purchase #6	$112.86	5.321%	$118.8653	$118.87	$118.85	$118.90
Purchase #7	$86.66	3.655%	$89.8274	$89.83	$89.85	$89.80
7 purchase totals =	$1,026.41		$1,132.2851	$1,132.29	$1,132.30	$1,132.40