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	$181.49	6.643%	$193.5464	$193.55	$193.55	$193.50
Purchase #2	$213.83	9.839%	$234.8687	$234.87	$234.85	$234.90
Purchase #3	$120.70	5.733%	$127.6197	$127.62	$127.60	$127.60
Purchase #4	$47.35	13.579%	$53.7797	$53.78	$53.80	$53.80
Purchase #5	$197.71	13.516%	$224.4325	$224.43	$224.45	$224.40
Purchase #6	$88.98	4.381%	$92.8782	$92.88	$92.90	$92.90
Purchase #7	$80.37	6.377%	$85.4952	$85.50	$85.50	$85.50
7 purchase totals =	$930.43		$1,012.6204	$1,012.63	$1,012.65	$1,012.60