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	$12.95	10.498%	$14.3095	$14.31	$14.30	$14.30
Purchase #2	$99.60	6.317%	$105.8917	$105.89	$105.90	$105.90
Purchase #3	$225.73	13.678%	$256.6053	$256.61	$256.60	$256.60
Purchase #4	$65.82	9.221%	$71.8893	$71.89	$71.90	$71.90
Purchase #5	$136.38	13.371%	$154.6154	$154.62	$154.60	$154.60
Purchase #6	$170.59	4.379%	$178.0601	$178.06	$178.05	$178.10
Purchase #7	$196.64	4.231%	$204.9598	$204.96	$204.95	$205.00
7 purchase totals =	$907.71		$986.3311	$986.34	$986.30	$986.40