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	$114.60	11.219%	$127.457	$127.46	$127.45	$127.50
Purchase #2	$94.52	8.411%	$102.4701	$102.47	$102.45	$102.50
Purchase #3	$63.28	13.295%	$71.6931	$71.69	$71.70	$71.70
Purchase #4	$166.83	11.114%	$185.3715	$185.37	$185.35	$185.40
Purchase #5	$137.28	5.277%	$144.5243	$144.52	$144.50	$144.50
Purchase #6	$221.56	11.363%	$246.7359	$246.74	$246.75	$246.70
Purchase #7	$149.63	13.760%	$170.2191	$170.22	$170.20	$170.20
7 purchase totals =	$947.70		$1,048.4710	$1,048.47	$1,048.40	$1,048.50