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	$182.94	4.816%	$191.7504	$191.75	$191.75	$191.80
Purchase #2	$182.46	5.611%	$192.6978	$192.70	$192.70	$192.70
Purchase #3	$140.68	3.557%	$145.684	$145.68	$145.70	$145.70
Purchase #4	$174.55	6.223%	$185.4122	$185.41	$185.40	$185.40
Purchase #5	$49.70	13.127%	$56.2241	$56.22	$56.20	$56.20
Purchase #6	$83.41	7.718%	$89.8476	$89.85	$89.85	$89.80
Purchase #7	$6.79	9.291%	$7.4209	$7.42	$7.40	$7.40
7 purchase totals =	$820.53		$869.0370	$869.03	$869.00	$869.00