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	$159.76	5.733%	$168.919	$168.92	$168.90	$168.90
Purchase #2	$36.82	3.796%	$38.2177	$38.22	$38.20	$38.20
Purchase #3	$250.49	6.219%	$266.068	$266.07	$266.05	$266.10
Purchase #4	$218.82	5.853%	$231.6275	$231.63	$231.65	$231.60
Purchase #5	$119.98	6.362%	$127.6131	$127.61	$127.60	$127.60
Purchase #6	$50.33	12.174%	$56.4572	$56.46	$56.45	$56.50
Purchase #7	$114.55	7.724%	$123.3978	$123.40	$123.40	$123.40
7 purchase totals =	$950.75		$1,012.3003	$1,012.31	$1,012.25	$1,012.30