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	$218.84	4.845%	$229.4428	$229.44	$229.45	$229.40
Purchase #2	$169.40	12.469%	$190.5225	$190.52	$190.50	$190.50
Purchase #3	$108.65	13.542%	$123.3634	$123.36	$123.35	$123.40
Purchase #4	$220.87	4.835%	$231.5491	$231.55	$231.55	$231.50
Purchase #5	$64.75	11.328%	$72.0849	$72.08	$72.10	$72.10
Purchase #6	$113.59	11.760%	$126.9482	$126.95	$126.95	$126.90
Purchase #7	$75.72	13.528%	$85.9634	$85.96	$85.95	$86.00
7 purchase totals =	$971.82		$1,059.8743	$1,059.86	$1,059.85	$1,059.80