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	$218.69	8.404%	$237.0687	$237.07	$237.05	$237.10
Purchase #2	$116.43	13.140%	$131.7289	$131.73	$131.75	$131.70
Purchase #3	$236.93	13.605%	$269.1643	$269.16	$269.15	$269.20
Purchase #4	$70.28	11.426%	$78.3102	$78.31	$78.30	$78.30
Purchase #5	$219.50	4.821%	$230.0821	$230.08	$230.10	$230.10
Purchase #6	$43.72	3.123%	$45.0854	$45.09	$45.10	$45.10
Purchase #7	$33.79	10.329%	$37.2802	$37.28	$37.30	$37.30
7 purchase totals =	$939.34		$1,028.7198	$1,028.72	$1,028.75	$1,028.80