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	$168.90	7.355%	$181.3226	$181.32	$181.30	$181.30
Purchase #2	$92.62	8.441%	$100.4381	$100.44	$100.45	$100.40
Purchase #3	$17.29	7.243%	$18.5423	$18.54	$18.55	$18.50
Purchase #4	$71.99	11.136%	$80.0068	$80.01	$80.00	$80.00
Purchase #5	$216.31	4.178%	$225.3474	$225.35	$225.35	$225.30
Purchase #6	$92.46	5.859%	$97.8772	$97.88	$97.90	$97.90
Purchase #7	$103.52	9.426%	$113.2778	$113.28	$113.30	$113.30
7 purchase totals =	$763.09		$816.8122	$816.82	$816.85	$816.70