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	$114.72	13.202%	$129.8653	$129.87	$129.85	$129.90
Purchase #2	$171.31	10.112%	$188.6329	$188.63	$188.65	$188.60
Purchase #3	$165.47	5.346%	$174.316	$174.32	$174.30	$174.30
Purchase #4	$205.99	4.633%	$215.5335	$215.53	$215.55	$215.50
Purchase #5	$127.89	12.511%	$143.8903	$143.89	$143.90	$143.90
Purchase #6	$100.45	4.424%	$104.8939	$104.89	$104.90	$104.90
Purchase #7	$50.75	9.150%	$55.3936	$55.39	$55.40	$55.40
7 purchase totals =	$936.58		$1,012.5255	$1,012.52	$1,012.55	$1,012.50