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	$81.51	8.638%	$88.5508	$88.55	$88.55	$88.60
Purchase #2	$108.69	4.698%	$113.7963	$113.80	$113.80	$113.80
Purchase #3	$233.92	12.628%	$263.4594	$263.46	$263.45	$263.50
Purchase #4	$29.56	6.546%	$31.495	$31.50	$31.50	$31.50
Purchase #5	$168.82	10.702%	$186.8871	$186.89	$186.90	$186.90
Purchase #6	$174.32	9.299%	$190.53	$190.53	$190.55	$190.50
Purchase #7	$9.91	5.814%	$10.4862	$10.49	$10.50	$10.50
7 purchase totals =	$806.73		$885.2048	$885.22	$885.25	$885.30