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	$172.58	13.757%	$196.3218	$196.32	$196.30	$196.30
Purchase #2	$167.32	5.165%	$175.9621	$175.96	$175.95	$176.00
Purchase #3	$86.82	4.346%	$90.5932	$90.59	$90.60	$90.60
Purchase #4	$115.73	7.416%	$124.3125	$124.31	$124.30	$124.30
Purchase #5	$13.75	5.484%	$14.5041	$14.50	$14.50	$14.50
Purchase #6	$148.67	13.866%	$169.2846	$169.28	$169.30	$169.30
Purchase #7	$20.59	13.712%	$23.4133	$23.41	$23.40	$23.40
7 purchase totals =	$725.46		$794.3916	$794.37	$794.35	$794.40