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	$177.96	10.360%	$196.3967	$196.40	$196.40	$196.40
Purchase #2	$102.43	7.211%	$109.8162	$109.82	$109.80	$109.80
Purchase #3	$94.72	11.366%	$105.4859	$105.49	$105.50	$105.50
Purchase #4	$83.91	7.756%	$90.4181	$90.42	$90.40	$90.40
Purchase #5	$13.29	9.738%	$14.5842	$14.58	$14.60	$14.60
Purchase #6	$226.50	7.351%	$243.15	$243.15	$243.15	$243.20
Purchase #7	$87.41	7.415%	$93.8915	$93.89	$93.90	$93.90
7 purchase totals =	$786.22		$853.7426	$853.75	$853.75	$853.80