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	$230.90	7.611%	$248.4738	$248.47	$248.45	$248.50
Purchase #2	$88.60	10.161%	$97.6026	$97.60	$97.60	$97.60
Purchase #3	$55.76	7.490%	$59.9364	$59.94	$59.95	$59.90
Purchase #4	$44.50	4.185%	$46.3623	$46.36	$46.35	$46.40
Purchase #5	$189.55	6.335%	$201.558	$201.56	$201.55	$201.60
Purchase #6	$143.25	12.242%	$160.7867	$160.79	$160.80	$160.80
Purchase #7	$118.81	7.188%	$127.3501	$127.35	$127.35	$127.40
7 purchase totals =	$871.37		$942.0699	$942.07	$942.05	$942.20