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	$63.29	3.818%	$65.7064	$65.71	$65.70	$65.70
Purchase #2	$202.58	11.275%	$225.4209	$225.42	$225.40	$225.40
Purchase #3	$155.80	3.476%	$161.2156	$161.22	$161.20	$161.20
Purchase #4	$220.41	5.180%	$231.8272	$231.83	$231.85	$231.80
Purchase #5	$210.42	5.157%	$221.2714	$221.27	$221.25	$221.30
Purchase #6	$83.99	8.172%	$90.8537	$90.85	$90.85	$90.90
Purchase #7	$78.47	13.849%	$89.3373	$89.34	$89.35	$89.30
7 purchase totals =	$1,014.96		$1,085.6325	$1,085.64	$1,085.60	$1,085.60