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	$188.47	10.573%	$208.3969	$208.40	$208.40	$208.40
Purchase #2	$200.53	10.400%	$221.3851	$221.39	$221.40	$221.40
Purchase #3	$144.85	9.451%	$158.5398	$158.54	$158.55	$158.50
Purchase #4	$134.46	3.591%	$139.2885	$139.29	$139.30	$139.30
Purchase #5	$87.28	8.716%	$94.8873	$94.89	$94.90	$94.90
Purchase #6	$224.61	7.482%	$241.4153	$241.42	$241.40	$241.40
Purchase #7	$30.72	8.807%	$33.4255	$33.43	$33.45	$33.40
7 purchase totals =	$1,010.92		$1,097.3384	$1,097.36	$1,097.40	$1,097.30