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	$243.47	11.778%	$272.1459	$272.15	$272.15	$272.10
Purchase #2	$234.46	10.327%	$258.6727	$258.67	$258.65	$258.70
Purchase #3	$114.29	11.132%	$127.0128	$127.01	$127.00	$127.00
Purchase #4	$78.50	10.786%	$86.967	$86.97	$86.95	$87.00
Purchase #5	$104.50	6.598%	$111.3949	$111.39	$111.40	$111.40
Purchase #6	$222.35	5.345%	$234.2346	$234.23	$234.25	$234.20
Purchase #7	$107.66	6.399%	$114.5492	$114.55	$114.55	$114.50
7 purchase totals =	$1,105.23		$1,204.9771	$1,204.97	$1,204.95	$1,204.90