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	$160.83	8.867%	$175.0908	$175.09	$175.10	$175.10
Purchase #2	$33.67	8.449%	$36.5148	$36.51	$36.50	$36.50
Purchase #3	$220.26	5.150%	$231.6034	$231.60	$231.60	$231.60
Purchase #4	$99.71	11.696%	$111.3721	$111.37	$111.35	$111.40
Purchase #5	$38.46	12.463%	$43.2533	$43.25	$43.25	$43.30
Purchase #6	$80.49	11.332%	$89.6111	$89.61	$89.60	$89.60
Purchase #7	$166.52	11.113%	$185.0254	$185.03	$185.05	$185.00
7 purchase totals =	$799.94		$872.4709	$872.46	$872.45	$872.50