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	$96.87	4.196%	$100.9347	$100.93	$100.95	$100.90
Purchase #2	$90.70	7.514%	$97.5152	$97.52	$97.50	$97.50
Purchase #3	$132.95	4.709%	$139.2106	$139.21	$139.20	$139.20
Purchase #4	$210.73	9.214%	$230.1467	$230.15	$230.15	$230.10
Purchase #5	$175.93	11.696%	$196.5068	$196.51	$196.50	$196.50
Purchase #6	$245.87	13.765%	$279.714	$279.71	$279.70	$279.70
Purchase #7	$54.41	6.175%	$57.7698	$57.77	$57.75	$57.80
7 purchase totals =	$1,007.46		$1,101.7978	$1,101.80	$1,101.75	$1,101.70