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	$239.95	10.269%	$264.5905	$264.59	$264.60	$264.60
Purchase #2	$151.54	9.131%	$165.3771	$165.38	$165.40	$165.40
Purchase #3	$220.79	3.398%	$228.2924	$228.29	$228.30	$228.30
Purchase #4	$158.95	13.678%	$180.6912	$180.69	$180.70	$180.70
Purchase #5	$171.53	6.397%	$182.5028	$182.50	$182.50	$182.50
Purchase #6	$112.42	6.294%	$119.4957	$119.50	$119.50	$119.50
Purchase #7	$78.72	9.658%	$86.3228	$86.32	$86.30	$86.30
7 purchase totals =	$1,133.90		$1,227.2725	$1,227.27	$1,227.30	$1,227.30