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	$114.71	3.392%	$118.601	$118.60	$118.60	$118.60
Purchase #2	$111.70	7.159%	$119.6966	$119.70	$119.70	$119.70
Purchase #3	$94.32	9.701%	$103.47	$103.47	$103.45	$103.50
Purchase #4	$70.85	13.696%	$80.5536	$80.55	$80.55	$80.60
Purchase #5	$35.73	3.137%	$36.8509	$36.85	$36.85	$36.90
Purchase #6	$86.33	11.833%	$96.5454	$96.55	$96.55	$96.50
Purchase #7	$43.50	13.870%	$49.5335	$49.53	$49.55	$49.50
7 purchase totals =	$557.14		$605.2510	$605.25	$605.25	$605.30