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	$226.79	6.683%	$241.9464	$241.95	$241.95	$241.90
Purchase #2	$41.26	3.159%	$42.5634	$42.56	$42.55	$42.60
Purchase #3	$63.82	12.478%	$71.7835	$71.78	$71.80	$71.80
Purchase #4	$56.70	5.315%	$59.7136	$59.71	$59.70	$59.70
Purchase #5	$113.28	5.576%	$119.5965	$119.60	$119.60	$119.60
Purchase #6	$77.71	9.291%	$84.93	$84.93	$84.95	$84.90
Purchase #7	$180.26	4.525%	$188.4168	$188.42	$188.40	$188.40
7 purchase totals =	$759.82		$808.9502	$808.95	$808.95	$808.90