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	$128.31	10.355%	$141.5965	$141.60	$141.60	$141.60
Purchase #2	$43.40	5.284%	$45.6933	$45.69	$45.70	$45.70
Purchase #3	$235.43	13.576%	$267.392	$267.39	$267.40	$267.40
Purchase #4	$214.28	7.794%	$230.981	$230.98	$231.00	$231.00
Purchase #5	$172.86	7.874%	$186.471	$186.47	$186.45	$186.50
Purchase #6	$145.75	12.688%	$164.2428	$164.24	$164.25	$164.20
Purchase #7	$85.29	8.328%	$92.393	$92.39	$92.40	$92.40
7 purchase totals =	$1,025.32		$1,128.7696	$1,128.76	$1,128.80	$1,128.80