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	$55.95	12.586%	$62.9919	$62.99	$63.00	$63.00
Purchase #2	$112.45	13.620%	$127.7657	$127.77	$127.75	$127.80
Purchase #3	$50.84	5.152%	$53.4593	$53.46	$53.45	$53.50
Purchase #4	$159.47	12.254%	$179.0115	$179.01	$179.00	$179.00
Purchase #5	$231.79	12.356%	$260.43	$260.43	$260.45	$260.40
Purchase #6	$187.85	9.594%	$205.8723	$205.87	$205.85	$205.90
Purchase #7	$167.77	6.309%	$178.3546	$178.35	$178.35	$178.40
7 purchase totals =	$966.12		$1,067.8853	$1,067.88	$1,067.85	$1,068.00