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	$154.58	12.226%	$173.479	$173.48	$173.50	$173.50
Purchase #2	$234.44	13.291%	$265.5994	$265.60	$265.60	$265.60
Purchase #3	$96.69	8.569%	$104.9754	$104.98	$105.00	$105.00
Purchase #4	$112.44	13.417%	$127.5261	$127.53	$127.55	$127.50
Purchase #5	$83.68	3.828%	$86.8833	$86.88	$86.90	$86.90
Purchase #6	$119.79	9.227%	$130.843	$130.84	$130.85	$130.80
Purchase #7	$126.67	13.355%	$143.5868	$143.59	$143.60	$143.60
7 purchase totals =	$928.29		$1,032.8930	$1,032.90	$1,033.00	$1,032.90