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	$216.59	5.229%	$227.9155	$227.92	$227.90	$227.90
Purchase #2	$165.35	9.816%	$181.5808	$181.58	$181.60	$181.60
Purchase #3	$106.92	10.423%	$118.0643	$118.06	$118.05	$118.10
Purchase #4	$118.55	11.329%	$131.9805	$131.98	$132.00	$132.00
Purchase #5	$51.28	10.186%	$56.5034	$56.50	$56.50	$56.50
Purchase #6	$199.87	6.818%	$213.4971	$213.50	$213.50	$213.50
Purchase #7	$162.85	4.812%	$170.6863	$170.69	$170.70	$170.70
7 purchase totals =	$1,021.41		$1,100.2279	$1,100.23	$1,100.25	$1,100.30