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	$199.59	13.354%	$226.2432	$226.24	$226.25	$226.20
Purchase #2	$109.73	12.373%	$123.3069	$123.31	$123.30	$123.30
Purchase #3	$91.71	11.853%	$102.5804	$102.58	$102.60	$102.60
Purchase #4	$155.68	11.219%	$173.1457	$173.15	$173.15	$173.10
Purchase #5	$112.80	10.200%	$124.3056	$124.31	$124.30	$124.30
Purchase #6	$173.27	7.801%	$186.7868	$186.79	$186.80	$186.80
Purchase #7	$69.54	4.673%	$72.7896	$72.79	$72.80	$72.80
7 purchase totals =	$912.32		$1,009.1582	$1,009.17	$1,009.20	$1,009.10