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	$111.85	10.153%	$123.2061	$123.21	$123.20	$123.20
Purchase #2	$219.35	4.769%	$229.8108	$229.81	$229.80	$229.80
Purchase #3	$99.79	5.758%	$105.5359	$105.54	$105.55	$105.50
Purchase #4	$15.82	5.321%	$16.6618	$16.66	$16.65	$16.70
Purchase #5	$239.47	13.482%	$271.7553	$271.76	$271.75	$271.80
Purchase #6	$161.58	13.448%	$183.3093	$183.31	$183.30	$183.30
Purchase #7	$183.69	6.874%	$196.3169	$196.32	$196.30	$196.30
7 purchase totals =	$1,031.55		$1,126.5961	$1,126.61	$1,126.55	$1,126.60