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	$218.62	6.688%	$233.2413	$233.24	$233.25	$233.20
Purchase #2	$54.41	4.577%	$56.9003	$56.90	$56.90	$56.90
Purchase #3	$249.94	13.625%	$283.9943	$283.99	$284.00	$284.00
Purchase #4	$186.40	7.578%	$200.5254	$200.53	$200.55	$200.50
Purchase #5	$176.54	5.399%	$186.0714	$186.07	$186.05	$186.10
Purchase #6	$18.66	11.731%	$20.849	$20.85	$20.85	$20.80
Purchase #7	$39.56	9.758%	$43.4203	$43.42	$43.40	$43.40
7 purchase totals =	$944.13		$1,025.0020	$1,025.00	$1,025.00	$1,024.90