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	$92.41	13.454%	$104.8428	$104.84	$104.85	$104.80
Purchase #2	$36.60	5.717%	$38.6924	$38.69	$38.70	$38.70
Purchase #3	$104.63	11.539%	$116.7033	$116.70	$116.70	$116.70
Purchase #4	$30.49	4.637%	$31.9038	$31.90	$31.90	$31.90
Purchase #5	$141.39	6.606%	$150.7302	$150.73	$150.75	$150.70
Purchase #6	$103.85	8.719%	$112.9047	$112.90	$112.90	$112.90
Purchase #7	$105.28	6.461%	$112.0821	$112.08	$112.10	$112.10
7 purchase totals =	$614.65		$667.8593	$667.84	$667.90	$667.80