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	$135.51	11.396%	$150.9527	$150.95	$150.95	$151.00
Purchase #2	$38.30	10.696%	$42.3966	$42.40	$42.40	$42.40
Purchase #3	$31.44	3.872%	$32.6574	$32.66	$32.65	$32.70
Purchase #4	$133.54	11.120%	$148.3896	$148.39	$148.40	$148.40
Purchase #5	$44.40	5.521%	$46.8513	$46.85	$46.85	$46.90
Purchase #6	$85.89	11.166%	$95.4805	$95.48	$95.50	$95.50
Purchase #7	$140.47	10.253%	$154.8724	$154.87	$154.85	$154.90
7 purchase totals =	$609.55		$671.6005	$671.60	$671.60	$671.80