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	$219.51	8.122%	$237.3386	$237.34	$237.35	$237.30
Purchase #2	$225.75	13.318%	$255.8154	$255.82	$255.80	$255.80
Purchase #3	$52.65	13.165%	$59.5814	$59.58	$59.60	$59.60
Purchase #4	$228.74	4.178%	$238.2968	$238.30	$238.30	$238.30
Purchase #5	$174.46	6.375%	$185.5818	$185.58	$185.60	$185.60
Purchase #6	$116.82	9.398%	$127.7987	$127.80	$127.80	$127.80
Purchase #7	$153.96	11.550%	$171.7424	$171.74	$171.75	$171.70
7 purchase totals =	$1,171.89		$1,276.1551	$1,276.16	$1,276.20	$1,276.10