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	$218.31	12.195%	$244.9329	$244.93	$244.95	$244.90
Purchase #2	$82.97	4.682%	$86.8547	$86.85	$86.85	$86.90
Purchase #3	$60.58	7.746%	$65.2725	$65.27	$65.25	$65.30
Purchase #4	$213.71	12.538%	$240.505	$240.51	$240.50	$240.50
Purchase #5	$105.82	3.721%	$109.7576	$109.76	$109.75	$109.80
Purchase #6	$81.32	6.759%	$86.8164	$86.82	$86.80	$86.80
Purchase #7	$105.48	12.432%	$118.5933	$118.59	$118.60	$118.60
7 purchase totals =	$868.19		$952.7324	$952.73	$952.70	$952.80