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	$112.76	12.872%	$127.2745	$127.27	$127.25	$127.30
Purchase #2	$232.96	12.685%	$262.511	$262.51	$262.50	$262.50
Purchase #3	$193.94	4.867%	$203.3791	$203.38	$203.40	$203.40
Purchase #4	$46.41	9.398%	$50.7716	$50.77	$50.75	$50.80
Purchase #5	$106.29	5.830%	$112.4867	$112.49	$112.50	$112.50
Purchase #6	$100.46	11.127%	$111.6382	$111.64	$111.65	$111.60
Purchase #7	$122.83	3.455%	$127.0738	$127.07	$127.05	$127.10
7 purchase totals =	$915.65		$995.1349	$995.13	$995.10	$995.20