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	$118.31	4.749%	$123.9285	$123.93	$123.95	$123.90
Purchase #2	$203.41	12.614%	$229.0681	$229.07	$229.05	$229.10
Purchase #3	$127.58	11.231%	$141.9085	$141.91	$141.90	$141.90
Purchase #4	$136.72	9.779%	$150.0898	$150.09	$150.10	$150.10
Purchase #5	$122.30	11.864%	$136.8097	$136.81	$136.80	$136.80
Purchase #6	$21.69	11.457%	$24.175	$24.18	$24.20	$24.20
Purchase #7	$237.76	11.640%	$265.4353	$265.44	$265.45	$265.40
7 purchase totals =	$967.77		$1,071.4149	$1,071.43	$1,071.45	$1,071.40