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	$41.77	8.590%	$45.358	$45.36	$45.35	$45.40
Purchase #2	$154.80	7.565%	$166.5106	$166.51	$166.50	$166.50
Purchase #3	$127.31	6.348%	$135.3916	$135.39	$135.40	$135.40
Purchase #4	$242.60	9.606%	$265.9042	$265.90	$265.90	$265.90
Purchase #5	$242.44	9.485%	$265.4354	$265.44	$265.45	$265.40
Purchase #6	$39.56	8.557%	$42.9451	$42.95	$42.95	$42.90
Purchase #7	$155.55	13.682%	$176.8324	$176.83	$176.85	$176.80
7 purchase totals =	$1,004.03		$1,098.3773	$1,098.38	$1,098.40	$1,098.30