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	$159.83	8.763%	$173.8359	$173.84	$173.85	$173.80
Purchase #2	$140.40	9.785%	$154.1381	$154.14	$154.15	$154.10
Purchase #3	$242.38	7.706%	$261.0578	$261.06	$261.05	$261.10
Purchase #4	$168.52	12.243%	$189.1519	$189.15	$189.15	$189.20
Purchase #5	$73.76	5.786%	$78.0278	$78.03	$78.05	$78.00
Purchase #6	$140.45	11.364%	$156.4107	$156.41	$156.40	$156.40
Purchase #7	$42.39	6.606%	$45.1903	$45.19	$45.20	$45.20
7 purchase totals =	$967.73		$1,057.8125	$1,057.82	$1,057.85	$1,057.80