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	$163.94	13.828%	$186.6096	$186.61	$186.60	$186.60
Purchase #2	$132.88	12.345%	$149.284	$149.28	$149.30	$149.30
Purchase #3	$128.74	10.837%	$142.6916	$142.69	$142.70	$142.70
Purchase #4	$194.54	5.644%	$205.5198	$205.52	$205.50	$205.50
Purchase #5	$152.38	12.728%	$171.7749	$171.77	$171.75	$171.80
Purchase #6	$94.33	7.422%	$101.3312	$101.33	$101.35	$101.30
Purchase #7	$86.50	4.805%	$90.6563	$90.66	$90.65	$90.70
7 purchase totals =	$953.31		$1,047.8674	$1,047.86	$1,047.85	$1,047.90