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	$245.87	7.126%	$263.3907	$263.39	$263.40	$263.40
Purchase #2	$240.28	10.656%	$265.8842	$265.88	$265.90	$265.90
Purchase #3	$23.56	9.778%	$25.8637	$25.86	$25.85	$25.90
Purchase #4	$164.91	4.470%	$172.2815	$172.28	$172.30	$172.30
Purchase #5	$11.40	6.724%	$12.1665	$12.17	$12.15	$12.20
Purchase #6	$63.91	11.583%	$71.3127	$71.31	$71.30	$71.30
Purchase #7	$85.95	12.842%	$96.9877	$96.99	$97.00	$97.00
7 purchase totals =	$835.88		$907.8870	$907.88	$907.90	$908.00