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	$20.25	10.604%	$22.3973	$22.40	$22.40	$22.40
Purchase #2	$150.51	6.633%	$160.4933	$160.49	$160.50	$160.50
Purchase #3	$45.84	3.745%	$47.5567	$47.56	$47.55	$47.60
Purchase #4	$179.64	9.273%	$196.298	$196.30	$196.30	$196.30
Purchase #5	$64.36	4.612%	$67.3283	$67.33	$67.35	$67.30
Purchase #6	$18.66	12.174%	$20.9317	$20.93	$20.95	$20.90
Purchase #7	$237.25	9.193%	$259.0604	$259.06	$259.05	$259.10
7 purchase totals =	$716.51		$774.0657	$774.07	$774.10	$774.10