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	$37.79	10.147%	$41.6246	$41.62	$41.60	$41.60
Purchase #2	$174.26	6.536%	$185.6496	$185.65	$185.65	$185.60
Purchase #3	$104.47	11.492%	$116.4757	$116.48	$116.50	$116.50
Purchase #4	$179.29	8.136%	$193.877	$193.88	$193.90	$193.90
Purchase #5	$108.82	9.708%	$119.3842	$119.38	$119.40	$119.40
Purchase #6	$61.75	7.444%	$66.3467	$66.35	$66.35	$66.30
Purchase #7	$34.86	6.343%	$37.0712	$37.07	$37.05	$37.10
7 purchase totals =	$701.24		$760.4290	$760.43	$760.45	$760.40