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	$157.41	11.238%	$175.0997	$175.10	$175.10	$175.10
Purchase #2	$58.79	10.330%	$64.863	$64.86	$64.85	$64.90
Purchase #3	$246.29	6.420%	$262.1018	$262.10	$262.10	$262.10
Purchase #4	$118.29	7.857%	$127.584	$127.58	$127.60	$127.60
Purchase #5	$43.90	8.847%	$47.7838	$47.78	$47.80	$47.80
Purchase #6	$100.28	12.252%	$112.5663	$112.57	$112.55	$112.60
Purchase #7	$94.50	10.573%	$104.4915	$104.49	$104.50	$104.50
7 purchase totals =	$819.46		$894.4901	$894.48	$894.50	$894.60