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	$208.64	8.203%	$225.7547	$225.75	$225.75	$225.80
Purchase #2	$200.79	4.824%	$210.4761	$210.48	$210.50	$210.50
Purchase #3	$83.94	7.708%	$90.4101	$90.41	$90.40	$90.40
Purchase #4	$240.65	5.376%	$253.5873	$253.59	$253.60	$253.60
Purchase #5	$19.61	3.410%	$20.2787	$20.28	$20.30	$20.30
Purchase #6	$107.78	8.143%	$116.5565	$116.56	$116.55	$116.60
Purchase #7	$76.90	4.421%	$80.2997	$80.30	$80.30	$80.30
7 purchase totals =	$938.31		$997.3631	$997.37	$997.40	$997.50