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	$169.97	3.306%	$175.5892	$175.59	$175.60	$175.60
Purchase #2	$24.88	7.241%	$26.6816	$26.68	$26.70	$26.70
Purchase #3	$80.52	11.110%	$89.4658	$89.47	$89.45	$89.50
Purchase #4	$104.47	12.874%	$117.9195	$117.92	$117.90	$117.90
Purchase #5	$172.78	10.119%	$190.2636	$190.26	$190.25	$190.30
Purchase #6	$99.47	5.859%	$105.2979	$105.30	$105.30	$105.30
Purchase #7	$30.76	6.708%	$32.8234	$32.82	$32.80	$32.80
7 purchase totals =	$682.85		$738.0410	$738.04	$738.00	$738.10