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	$131.81	7.678%	$141.9304	$141.93	$141.95	$141.90
Purchase #2	$196.60	5.750%	$207.9045	$207.90	$207.90	$207.90
Purchase #3	$51.25	6.836%	$54.7535	$54.75	$54.75	$54.80
Purchase #4	$105.42	6.701%	$112.4842	$112.48	$112.50	$112.50
Purchase #5	$150.79	3.808%	$156.5321	$156.53	$156.55	$156.50
Purchase #6	$137.87	13.578%	$156.59	$156.59	$156.60	$156.60
Purchase #7	$119.43	11.638%	$133.3293	$133.33	$133.35	$133.30
7 purchase totals =	$893.17		$963.5240	$963.51	$963.60	$963.50