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	$114.69	5.122%	$120.5644	$120.56	$120.55	$120.60
Purchase #2	$244.87	4.131%	$254.9856	$254.99	$255.00	$255.00
Purchase #3	$229.94	11.521%	$256.4314	$256.43	$256.45	$256.40
Purchase #4	$227.96	11.129%	$253.3297	$253.33	$253.35	$253.30
Purchase #5	$60.48	10.610%	$66.8969	$66.90	$66.90	$66.90
Purchase #6	$38.28	10.816%	$42.4204	$42.42	$42.40	$42.40
Purchase #7	$49.70	3.318%	$51.349	$51.35	$51.35	$51.30
7 purchase totals =	$965.92		$1,045.9774	$1,045.98	$1,046.00	$1,045.90