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	$36.25	3.759%	$37.6126	$37.61	$37.60	$37.60
Purchase #2	$43.77	8.565%	$47.5189	$47.52	$47.50	$47.50
Purchase #3	$16.71	7.662%	$17.9903	$17.99	$18.00	$18.00
Purchase #4	$50.40	12.530%	$56.7151	$56.72	$56.70	$56.70
Purchase #5	$82.42	9.324%	$90.1048	$90.10	$90.10	$90.10
Purchase #6	$52.70	5.465%	$55.5801	$55.58	$55.60	$55.60
Purchase #7	$178.51	10.108%	$196.5538	$196.55	$196.55	$196.60
7 purchase totals =	$460.76		$502.0756	$502.07	$502.05	$502.10