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	$118.72	4.345%	$123.8784	$123.88	$123.90	$123.90
Purchase #2	$103.30	13.602%	$117.3509	$117.35	$117.35	$117.40
Purchase #3	$67.66	7.229%	$72.5511	$72.55	$72.55	$72.60
Purchase #4	$214.96	3.653%	$222.8125	$222.81	$222.80	$222.80
Purchase #5	$97.49	7.801%	$105.0952	$105.10	$105.10	$105.10
Purchase #6	$37.72	3.136%	$38.9029	$38.90	$38.90	$38.90
Purchase #7	$211.27	3.165%	$217.9567	$217.96	$217.95	$218.00
7 purchase totals =	$851.12		$898.5477	$898.55	$898.55	$898.70