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	$184.47	6.391%	$196.2595	$196.26	$196.25	$196.30
Purchase #2	$96.88	3.297%	$100.0741	$100.07	$100.05	$100.10
Purchase #3	$192.43	5.635%	$203.2734	$203.27	$203.25	$203.30
Purchase #4	$23.85	10.758%	$26.4158	$26.42	$26.40	$26.40
Purchase #5	$51.97	13.533%	$59.0031	$59.00	$59.00	$59.00
Purchase #6	$62.88	4.731%	$65.8549	$65.85	$65.85	$65.90
Purchase #7	$121.85	9.482%	$133.4038	$133.40	$133.40	$133.40
7 purchase totals =	$734.33		$784.2846	$784.27	$784.20	$784.40