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	$55.49	7.601%	$59.7078	$59.71	$59.70	$59.70
Purchase #2	$118.62	7.389%	$127.3848	$127.38	$127.40	$127.40
Purchase #3	$43.26	7.481%	$46.4963	$46.50	$46.50	$46.50
Purchase #4	$172.30	4.713%	$180.4205	$180.42	$180.40	$180.40
Purchase #5	$116.56	12.568%	$131.2093	$131.21	$131.20	$131.20
Purchase #6	$152.38	5.492%	$160.7487	$160.75	$160.75	$160.70
Purchase #7	$230.43	5.670%	$243.4954	$243.50	$243.50	$243.50
7 purchase totals =	$889.04		$949.4628	$949.47	$949.45	$949.40