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	$218.60	10.473%	$241.494	$241.49	$241.50	$241.50
Purchase #2	$143.93	8.471%	$156.1223	$156.12	$156.10	$156.10
Purchase #3	$218.38	10.297%	$240.8666	$240.87	$240.85	$240.90
Purchase #4	$126.88	4.323%	$132.365	$132.37	$132.35	$132.40
Purchase #5	$73.33	13.555%	$83.2699	$83.27	$83.25	$83.30
Purchase #6	$133.50	13.295%	$151.2488	$151.25	$151.25	$151.20
Purchase #7	$169.89	13.673%	$193.1191	$193.12	$193.10	$193.10
7 purchase totals =	$1,084.51		$1,198.4857	$1,198.49	$1,198.40	$1,198.50