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	$82.43	8.714%	$89.613	$89.61	$89.60	$89.60
Purchase #2	$27.89	5.673%	$29.4722	$29.47	$29.45	$29.50
Purchase #3	$150.43	7.374%	$161.5227	$161.52	$161.50	$161.50
Purchase #4	$23.77	7.134%	$25.4658	$25.47	$25.45	$25.50
Purchase #5	$188.59	3.267%	$194.7512	$194.75	$194.75	$194.80
Purchase #6	$177.51	4.465%	$185.4358	$185.44	$185.45	$185.40
Purchase #7	$51.50	10.438%	$56.8756	$56.88	$56.90	$56.90
7 purchase totals =	$702.12		$743.1363	$743.14	$743.10	$743.20