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	$50.63	7.571%	$54.4632	$54.46	$54.45	$54.50
Purchase #2	$85.98	4.123%	$89.525	$89.53	$89.55	$89.50
Purchase #3	$137.54	4.669%	$143.9617	$143.96	$143.95	$144.00
Purchase #4	$198.40	7.604%	$213.4863	$213.49	$213.50	$213.50
Purchase #5	$228.46	9.557%	$250.2939	$250.29	$250.30	$250.30
Purchase #6	$180.78	5.209%	$190.1968	$190.20	$190.20	$190.20
Purchase #7	$58.29	13.733%	$66.295	$66.30	$66.30	$66.30
7 purchase totals =	$940.08		$1,008.2219	$1,008.23	$1,008.25	$1,008.30