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	$13.91	5.860%	$14.7251	$14.73	$14.75	$14.70
Purchase #2	$112.40	10.547%	$124.2548	$124.25	$124.25	$124.30
Purchase #3	$117.85	11.258%	$131.1176	$131.12	$131.10	$131.10
Purchase #4	$154.66	8.451%	$167.7303	$167.73	$167.75	$167.70
Purchase #5	$81.77	6.151%	$86.7997	$86.80	$86.80	$86.80
Purchase #6	$45.91	13.516%	$52.1152	$52.12	$52.10	$52.10
Purchase #7	$77.73	10.557%	$85.936	$85.94	$85.95	$85.90
7 purchase totals =	$604.23		$662.6787	$662.69	$662.70	$662.60