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	$52.88	11.594%	$59.0109	$59.01	$59.00	$59.00
Purchase #2	$27.90	7.234%	$29.9183	$29.92	$29.90	$29.90
Purchase #3	$63.65	4.445%	$66.4792	$66.48	$66.50	$66.50
Purchase #4	$212.69	11.535%	$237.2238	$237.22	$237.20	$237.20
Purchase #5	$76.26	8.705%	$82.8984	$82.90	$82.90	$82.90
Purchase #6	$224.85	12.756%	$253.5319	$253.53	$253.55	$253.50
Purchase #7	$129.36	7.763%	$139.4022	$139.40	$139.40	$139.40
7 purchase totals =	$787.59		$868.4647	$868.46	$868.45	$868.40