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	$60.93	12.297%	$68.4226	$68.42	$68.40	$68.40
Purchase #2	$189.67	3.808%	$196.8926	$196.89	$196.90	$196.90
Purchase #3	$32.56	5.755%	$34.4338	$34.43	$34.45	$34.40
Purchase #4	$23.77	3.160%	$24.5211	$24.52	$24.50	$24.50
Purchase #5	$108.32	7.870%	$116.8448	$116.84	$116.85	$116.80
Purchase #6	$171.62	5.225%	$180.5871	$180.59	$180.60	$180.60
Purchase #7	$28.39	11.816%	$31.7446	$31.74	$31.75	$31.70
7 purchase totals =	$615.26		$653.4466	$653.43	$653.45	$653.30