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	$163.43	9.270%	$178.58	$178.58	$178.60	$178.60
Purchase #2	$156.54	3.639%	$162.2365	$162.24	$162.25	$162.20
Purchase #3	$189.37	10.833%	$209.8845	$209.88	$209.90	$209.90
Purchase #4	$132.94	5.769%	$140.6093	$140.61	$140.60	$140.60
Purchase #5	$87.40	10.436%	$96.5211	$96.52	$96.50	$96.50
Purchase #6	$90.61	7.374%	$97.2916	$97.29	$97.30	$97.30
Purchase #7	$241.48	8.817%	$262.7713	$262.77	$262.75	$262.80
7 purchase totals =	$1,061.77		$1,147.8943	$1,147.89	$1,147.90	$1,147.90