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	$229.49	13.269%	$259.941	$259.94	$259.95	$259.90
Purchase #2	$37.40	13.429%	$42.4224	$42.42	$42.40	$42.40
Purchase #3	$189.93	3.224%	$196.0533	$196.05	$196.05	$196.10
Purchase #4	$182.76	6.577%	$194.7801	$194.78	$194.80	$194.80
Purchase #5	$181.93	9.273%	$198.8004	$198.80	$198.80	$198.80
Purchase #6	$132.43	9.140%	$144.5341	$144.53	$144.55	$144.50
Purchase #7	$174.84	7.639%	$188.196	$188.20	$188.20	$188.20
7 purchase totals =	$1,128.78		$1,224.7273	$1,224.72	$1,224.75	$1,224.70