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	$66.30	10.549%	$73.294	$73.29	$73.30	$73.30
Purchase #2	$246.61	6.711%	$263.16	$263.16	$263.15	$263.20
Purchase #3	$198.31	10.670%	$219.4697	$219.47	$219.45	$219.50
Purchase #4	$84.27	9.179%	$92.0051	$92.01	$92.00	$92.00
Purchase #5	$134.83	7.656%	$145.1526	$145.15	$145.15	$145.20
Purchase #6	$49.67	7.874%	$53.581	$53.58	$53.60	$53.60
Purchase #7	$80.46	5.803%	$85.1291	$85.13	$85.15	$85.10
7 purchase totals =	$860.45		$931.7915	$931.79	$931.80	$931.90