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	$104.84	7.506%	$112.7093	$112.71	$112.70	$112.70
Purchase #2	$175.71	7.634%	$189.1237	$189.12	$189.10	$189.10
Purchase #3	$127.86	12.782%	$144.2031	$144.20	$144.20	$144.20
Purchase #4	$134.95	6.236%	$143.3655	$143.37	$143.35	$143.40
Purchase #5	$115.61	3.159%	$119.2621	$119.26	$119.25	$119.30
Purchase #6	$115.85	6.183%	$123.013	$123.01	$123.00	$123.00
Purchase #7	$155.42	10.755%	$172.1354	$172.14	$172.15	$172.10
7 purchase totals =	$930.24		$1,003.8121	$1,003.81	$1,003.75	$1,003.80