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	$58.77	12.220%	$65.9517	$65.95	$65.95	$66.00
Purchase #2	$247.58	3.374%	$255.9333	$255.93	$255.95	$255.90
Purchase #3	$162.70	5.461%	$171.585	$171.59	$171.60	$171.60
Purchase #4	$245.36	8.629%	$266.5321	$266.53	$266.55	$266.50
Purchase #5	$113.25	13.447%	$128.4787	$128.48	$128.50	$128.50
Purchase #6	$79.25	9.428%	$86.7217	$86.72	$86.70	$86.70
Purchase #7	$73.75	11.439%	$82.1863	$82.19	$82.20	$82.20
7 purchase totals =	$980.66		$1,057.3888	$1,057.39	$1,057.45	$1,057.40