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	$100.47	11.617%	$112.1416	$112.14	$112.15	$112.10
Purchase #2	$35.34	8.642%	$38.3941	$38.39	$38.40	$38.40
Purchase #3	$80.73	11.367%	$89.9066	$89.91	$89.90	$89.90
Purchase #4	$128.53	12.199%	$144.2094	$144.21	$144.20	$144.20
Purchase #5	$208.34	10.388%	$229.9824	$229.98	$230.00	$230.00
Purchase #6	$239.47	6.654%	$255.4043	$255.40	$255.40	$255.40
Purchase #7	$240.47	13.395%	$272.681	$272.68	$272.70	$272.70
7 purchase totals =	$1,033.35		$1,142.7194	$1,142.71	$1,142.75	$1,142.70