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	$136.28	6.308%	$144.8765	$144.88	$144.90	$144.90
Purchase #2	$203.29	11.612%	$226.896	$226.90	$226.90	$226.90
Purchase #3	$247.48	11.360%	$275.5937	$275.59	$275.60	$275.60
Purchase #4	$69.87	3.598%	$72.3839	$72.38	$72.40	$72.40
Purchase #5	$74.34	13.519%	$84.39	$84.39	$84.40	$84.40
Purchase #6	$131.88	12.520%	$148.3914	$148.39	$148.40	$148.40
Purchase #7	$54.98	12.196%	$61.6854	$61.69	$61.70	$61.70
7 purchase totals =	$918.12		$1,014.2169	$1,014.22	$1,014.30	$1,014.30