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	$130.45	13.319%	$147.8246	$147.82	$147.80	$147.80
Purchase #2	$230.60	4.523%	$241.03	$241.03	$241.05	$241.00
Purchase #3	$150.56	9.384%	$164.6886	$164.69	$164.70	$164.70
Purchase #4	$11.77	5.678%	$12.4383	$12.44	$12.45	$12.40
Purchase #5	$184.69	7.223%	$198.0302	$198.03	$198.05	$198.00
Purchase #6	$59.96	4.818%	$62.8489	$62.85	$62.85	$62.80
Purchase #7	$186.75	13.769%	$212.4636	$212.46	$212.45	$212.50
7 purchase totals =	$954.78		$1,039.3242	$1,039.32	$1,039.35	$1,039.20