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	$119.25	8.671%	$129.5902	$129.59	$129.60	$129.60
Purchase #2	$27.88	12.450%	$31.3511	$31.35	$31.35	$31.40
Purchase #3	$50.51	9.112%	$55.1125	$55.11	$55.10	$55.10
Purchase #4	$89.66	11.628%	$100.0857	$100.09	$100.10	$100.10
Purchase #5	$88.87	13.565%	$100.9252	$100.93	$100.95	$100.90
Purchase #6	$55.26	7.839%	$59.5918	$59.59	$59.60	$59.60
Purchase #7	$239.92	8.478%	$260.2604	$260.26	$260.25	$260.30
7 purchase totals =	$671.35		$736.9169	$736.92	$736.95	$737.00