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	$94.99	8.183%	$102.763	$102.76	$102.75	$102.80
Purchase #2	$223.63	13.421%	$253.6434	$253.64	$253.65	$253.60
Purchase #3	$206.27	10.709%	$228.3595	$228.36	$228.35	$228.40
Purchase #4	$128.46	10.863%	$142.4146	$142.41	$142.40	$142.40
Purchase #5	$148.32	13.579%	$168.4604	$168.46	$168.45	$168.50
Purchase #6	$65.86	12.381%	$74.0141	$74.01	$74.00	$74.00
Purchase #7	$81.73	4.722%	$85.5893	$85.59	$85.60	$85.60
7 purchase totals =	$949.26		$1,055.2443	$1,055.23	$1,055.20	$1,055.30