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	$187.98	4.574%	$196.5782	$196.58	$196.60	$196.60
Purchase #2	$154.69	11.643%	$172.7006	$172.70	$172.70	$172.70
Purchase #3	$50.53	13.306%	$57.2535	$57.25	$57.25	$57.30
Purchase #4	$210.95	3.470%	$218.27	$218.27	$218.25	$218.30
Purchase #5	$176.28	3.495%	$182.441	$182.44	$182.45	$182.40
Purchase #6	$49.62	9.503%	$54.3354	$54.34	$54.35	$54.30
Purchase #7	$113.93	11.838%	$127.417	$127.42	$127.40	$127.40
7 purchase totals =	$943.98		$1,008.9957	$1,009.00	$1,009.00	$1,009.00