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	$81.86	4.561%	$85.5936	$85.59	$85.60	$85.60
Purchase #2	$24.97	3.727%	$25.9006	$25.90	$25.90	$25.90
Purchase #3	$162.66	5.201%	$171.1199	$171.12	$171.10	$171.10
Purchase #4	$49.89	12.274%	$56.0135	$56.01	$56.00	$56.00
Purchase #5	$60.53	9.611%	$66.3475	$66.35	$66.35	$66.30
Purchase #6	$105.33	3.657%	$109.1819	$109.18	$109.20	$109.20
Purchase #7	$47.75	6.687%	$50.943	$50.94	$50.95	$50.90
7 purchase totals =	$532.99		$565.1000	$565.09	$565.10	$565.00