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	$119.39	6.708%	$127.3987	$127.40	$127.40	$127.40
Purchase #2	$176.85	13.418%	$200.5797	$200.58	$200.60	$200.60
Purchase #3	$111.46	7.596%	$119.9265	$119.93	$119.95	$119.90
Purchase #4	$109.90	13.292%	$124.5079	$124.51	$124.50	$124.50
Purchase #5	$96.51	5.550%	$101.8663	$101.87	$101.85	$101.90
Purchase #6	$42.48	10.394%	$46.8954	$46.90	$46.90	$46.90
Purchase #7	$120.47	6.285%	$128.0415	$128.04	$128.05	$128.00
7 purchase totals =	$777.06		$849.2160	$849.23	$849.25	$849.20