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	$100.83	8.490%	$109.3905	$109.39	$109.40	$109.40
Purchase #2	$7.45	13.696%	$8.4704	$8.47	$8.45	$8.50
Purchase #3	$101.79	3.644%	$105.4992	$105.50	$105.50	$105.50
Purchase #4	$88.47	8.444%	$95.9404	$95.94	$95.95	$95.90
Purchase #5	$231.56	11.654%	$258.546	$258.55	$258.55	$258.50
Purchase #6	$67.28	8.131%	$72.7505	$72.75	$72.75	$72.80
Purchase #7	$82.35	5.675%	$87.0234	$87.02	$87.00	$87.00
7 purchase totals =	$679.73		$737.6204	$737.62	$737.60	$737.60