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	$239.27	5.174%	$251.6498	$251.65	$251.65	$251.60
Purchase #2	$140.72	7.217%	$150.8758	$150.88	$150.90	$150.90
Purchase #3	$248.93	5.635%	$262.9572	$262.96	$262.95	$263.00
Purchase #4	$17.96	6.557%	$19.1376	$19.14	$19.15	$19.10
Purchase #5	$34.42	11.282%	$38.3033	$38.30	$38.30	$38.30
Purchase #6	$175.66	11.872%	$196.5144	$196.51	$196.50	$196.50
Purchase #7	$80.52	9.721%	$88.3473	$88.35	$88.35	$88.30
7 purchase totals =	$937.48		$1,007.7854	$1,007.79	$1,007.80	$1,007.70