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	$219.88	9.839%	$241.514	$241.51	$241.50	$241.50
Purchase #2	$214.92	4.594%	$224.7934	$224.79	$224.80	$224.80
Purchase #3	$216.82	10.204%	$238.9443	$238.94	$238.95	$238.90
Purchase #4	$123.59	10.394%	$136.4359	$136.44	$136.45	$136.40
Purchase #5	$155.91	6.688%	$166.3373	$166.34	$166.35	$166.30
Purchase #6	$150.33	11.250%	$167.2421	$167.24	$167.25	$167.20
Purchase #7	$62.81	5.515%	$66.274	$66.27	$66.25	$66.30
7 purchase totals =	$1,144.26		$1,241.5410	$1,241.53	$1,241.55	$1,241.40