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	$239.71	12.444%	$269.5395	$269.54	$269.55	$269.50
Purchase #2	$29.96	5.435%	$31.5883	$31.59	$31.60	$31.60
Purchase #3	$76.91	8.414%	$83.3812	$83.38	$83.40	$83.40
Purchase #4	$203.80	10.731%	$225.6698	$225.67	$225.65	$225.70
Purchase #5	$225.39	13.355%	$255.4908	$255.49	$255.50	$255.50
Purchase #6	$138.82	9.575%	$152.112	$152.11	$152.10	$152.10
Purchase #7	$120.35	5.398%	$126.8465	$126.85	$126.85	$126.80
7 purchase totals =	$1,034.94		$1,144.6281	$1,144.63	$1,144.65	$1,144.60