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	$86.56	4.842%	$90.7512	$90.75	$90.75	$90.80
Purchase #2	$84.26	3.783%	$87.4476	$87.45	$87.45	$87.40
Purchase #3	$104.72	11.789%	$117.0654	$117.07	$117.05	$117.10
Purchase #4	$77.26	10.368%	$85.2703	$85.27	$85.25	$85.30
Purchase #5	$248.40	8.260%	$268.9178	$268.92	$268.90	$268.90
Purchase #6	$108.90	3.792%	$113.0295	$113.03	$113.05	$113.00
Purchase #7	$239.77	6.729%	$255.9041	$255.90	$255.90	$255.90
7 purchase totals =	$949.87		$1,018.3859	$1,018.39	$1,018.35	$1,018.40