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	$218.43	5.289%	$229.9828	$229.98	$230.00	$230.00
Purchase #2	$100.78	10.829%	$111.6935	$111.69	$111.70	$111.70
Purchase #3	$149.56	10.175%	$164.7777	$164.78	$164.80	$164.80
Purchase #4	$81.75	5.780%	$86.4752	$86.48	$86.50	$86.50
Purchase #5	$71.98	13.300%	$81.5533	$81.55	$81.55	$81.60
Purchase #6	$95.59	8.116%	$103.3481	$103.35	$103.35	$103.30
Purchase #7	$112.32	5.236%	$118.2011	$118.20	$118.20	$118.20
7 purchase totals =	$830.41		$896.0317	$896.03	$896.10	$896.10