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	$234.59	11.784%	$262.2341	$262.23	$262.25	$262.20
Purchase #2	$170.64	8.683%	$185.4567	$185.46	$185.45	$185.50
Purchase #3	$118.88	11.277%	$132.2861	$132.29	$132.30	$132.30
Purchase #4	$248.48	8.215%	$268.8926	$268.89	$268.90	$268.90
Purchase #5	$43.46	4.198%	$45.2845	$45.28	$45.30	$45.30
Purchase #6	$147.93	12.831%	$166.9109	$166.91	$166.90	$166.90
Purchase #7	$112.52	12.726%	$126.8393	$126.84	$126.85	$126.80
7 purchase totals =	$1,076.50		$1,187.9042	$1,187.90	$1,187.95	$1,187.90